View Filing Data

Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2017	Feb. 15, 2018	Jun. 30, 2017
Document and Entity Information
Entity Registrant Name	Essent Group Ltd.
Entity Central Index Key	0001448893
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 3,059,519,774
Entity Common Stock, Shares Outstanding		98,094,421
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Investments available for sale, at fair value
Fixed maturities (amortized cost: 2017 — $1,994,200; 2016 — $1,497,186)	$ 1,992,371	$ 1,482,754
Short-term investments (amortized cost: 2017 — $312,714; 2016 — $132,352)	312,694	132,348
Total investments	2,305,065	1,615,102
Cash	43,524	27,531
Accrued investment income	12,807	9,488
Accounts receivable	29,752	21,632
Deferred policy acquisition costs	15,354	13,400
Property and equipment (at cost, less accumulated depreciation of $50,466 in 2017 and $46,543 in 2016)	6,979	8,119
Prepaid federal income tax	252,157	181,272
Other assets	8,730	6,454
Total assets	2,674,368	1,882,998
Liabilities
Reserve for losses and LAE	46,850	28,142
Unearned premium reserve	259,672	219,616
Net deferred tax liability	127,636	142,587
Credit facility borrowings (at carrying value, less unamortized deferred costs of $1,409 in 2017 and $0 in 2016)	248,591	100,000
Securities purchases payable	14,999	14,999
Other accrued liabilities	36,184	33,881
Total liabilities	733,932	539,225
Commitments and contingencies (see Note 8)
Stockholders' Equity
Common Shares, $0.015 par value: Authorized - 233,333; issued and outstanding - 98,434 shares in 2017 and 93,105 shares in 2016	1,476	1,397
Additional paid-in capital	1,127,137	918,296
Accumulated other comprehensive loss	(3,252)	(12,255)
Retained earnings	815,075	436,335
Total stockholders' equity	1,940,436	1,343,773
Total liabilities and stockholders' equity	$ 2,674,368	$ 1,882,998

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Investments available for sale
Amortized cost	$ 2,306,914	$ 1,629,538
Property and equipment
Accumulated depreciation	50,466	46,543
Credit Facility Borrowings
Unamortized deferred costs	$ 1,409	$ 0
Stockholders' Equity
Common Shares, par value (in dollars per share)	$ 0.015	$ 0.015
Common Shares, authorized (in shares)	233,333,000	233,333,000
Common Shares, issued (in shares)	98,434,000	93,105,000
Common Shares, outstanding (in shares)	98,434,000	93,105,000
Fixed maturities
Investments available for sale
Amortized cost	$ 1,994,200	$ 1,497,186
Short-term investments
Investments available for sale
Amortized cost	$ 312,714	$ 132,352

Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Net premiums written	$ 570,186	$ 441,278	$ 370,568
Increase in unearned premiums	(40,056)	(18,571)	(44,097)
Net premiums earned	530,130	422,707	326,471
Net investment income	40,226	27,890	19,885
Realized investment gains, net	2,015	1,934	2,554
Other income	4,140	5,727	4,380
Total revenues	576,511	458,258	353,290
Losses and expenses:
Provision for losses and LAE	27,232	15,525	11,905
Other underwriting and operating expenses	145,533	130,425	112,987
Interest expense	5,178	426	0
Total losses and expenses	177,943	146,376	124,892
Income before income taxes	398,568	311,882	228,398
Income tax expense	18,821	89,276	71,067
Net income	$ 379,747	$ 222,606	$ 157,331
Earnings per share:
Basic (in dollars per share)	$ 4.07	$ 2.45	$ 1.74
Diluted (in dollars per share)	$ 3.99	$ 2.41	$ 1.72
Weighted average common shares outstanding:
Basic (in shares)	93,330	90,913	90,351
Diluted (in shares)	95,211	92,245	91,738
Net income	$ 379,747	$ 222,606	$ 157,331
Other comprehensive income (loss):
Change in unrealized appreciation (depreciation) of investments, net of tax expense (benefit) of $4,519 in 2017, ($2,941) in 2016 and ($1,285) in 2015	8,068	(12,156)	(4,766)
Total other comprehensive income (loss)	8,068	(12,156)	(4,766)
Comprehensive income	$ 387,815	$ 210,450	$ 152,565

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Change in unrealized appreciation (depreciation) of investments, tax expense (benefit)	$ 4,519	$ (2,941)	$ (1,285)

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Shares	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Treasury Stock
Stockholders equity, beginning of period at Dec. 31, 2014	$ 955,738	$ 1,388	$ 893,285	$ 4,667	$ 56,398	$ 0
Changes in Stockholders' Equity
Net income	157,331				157,331
Other comprehensive income (loss)	(4,766)			(4,766)
Issuance of management incentive shares		6	(6)
Forfeiture of management incentive shares		(1)	1
Stock-based compensation expense	13,633		13,633
Excess tax benefits from stock-based compensation expense	2,420		2,420
Treasury stock acquired	(5,168)					(5,168)
Cancellation of treasury stock		(3)	(5,165)			5,168
Other equity transactions	53		53
Stockholders equity, end of period at Dec. 31, 2015	1,119,241	1,390	904,221	(99)	213,729	0
Changes in Stockholders' Equity
Net income	222,606				222,606
Other comprehensive income (loss)	(12,156)			(12,156)
Issuance of management incentive shares		10	(10)
Forfeiture of management incentive shares		0	0
Stock-based compensation expense	16,881		16,881
Excess tax benefits from stock-based compensation expense	1,083		1,083
Treasury stock acquired	(4,024)					(4,024)
Cancellation of treasury stock		(3)	(4,021)			4,024
Other equity transactions	142		142
Stockholders equity, end of period at Dec. 31, 2016	1,343,773	1,397	918,296	(12,255)	436,335	0
Changes in Stockholders' Equity
Cumulative effect of ASU 2016-09 adoption	39		111		(72)
Net income	379,747				379,747
Other comprehensive income (loss)	8,068			8,068
Issuance of Common Shares, net of issuance cost of $1,802	197,698	75	197,623
Issuance of management incentive shares		8	(8)
Stock-based compensation expense	18,688		18,688
Treasury stock acquired	(7,577)					(7,577)
Cancellation of treasury stock		(4)	(7,573)			7,577
Reclassification of certain income tax effects resulting from tax reform				935	(935)
Stockholders equity, end of period at Dec. 31, 2017	$ 1,940,436	$ 1,476	$ 1,127,137	$ (3,252)	$ 815,075	$ 0

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Statement of Stockholders' Equity [Abstract]
Common stock, issuance cost	$ 1,802

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities
Net income	$ 379,747	$ 222,606	$ 157,331
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on the sale of investments, net	(2,015)	(1,934)	(2,554)
Depreciation and amortization	3,923	4,064	3,219
Stock-based compensation expense	18,688	16,881	13,633
Amortization of premium on investment securities	12,038	10,486	10,004
Deferred income tax provision	(19,431)	57,564	52,157
Change in:
Accrued investment income	(3,319)	(1,720)	(2,020)
Accounts receivable	(8,160)	(4,955)	(2,828)
Deferred policy acquisition costs	(1,954)	(1,871)	(1,932)
Prepaid federal income tax	(70,885)	(61,860)	(59,739)
Other assets	(1,408)	(526)	(724)
Reserve for losses and LAE	18,708	10,382	9,333
Unearned premium reserve	40,056	18,571	44,097
Other accrued liabilities	2,585	6,871	6,582
Net cash provided by operating activities	368,573	274,559	226,559
Investing Activities
Net change in short-term investments	(180,346)	(46,352)	124,692
Purchase of investments available for sale	(833,298)	(656,768)	(798,891)
Proceeds from maturity of investments available for sale	71,908	27,186	8,613
Proceeds from sales of investments available for sale	254,377	313,780	449,834
Purchase of property and equipment	(2,783)	(3,162)	(4,960)
Net cash used in investing activities	(690,142)	(365,316)	(220,712)
Financing Activities
Issuance of common shares, net of costs	197,829	0	(537)
Credit facility borrowings	200,000	100,000	0
Credit facility repayments	(50,000)	0	0
Treasury stock acquired	(7,577)	(4,024)	(5,168)
Payment of issuance costs for credit facility	(2,690)	(2,436)	0
Other financing activities	0	142	53
Net cash provided by (used in) financing activities	337,562	93,682	(5,652)
Net increase in cash	15,993	2,925	195
Cash at beginning of year	27,531	24,606	24,411
Cash at end of year	43,524	27,531	24,606
Supplemental Disclosure of Cash Flow Information
Income tax payments	(40,300)	(30,800)	(15,500)
Interest payments	$ (4,685)	$ (324)	$ 0

Nature of Operations and Basis of Presentation	12 Months Ended
Nature of Operations and Basis of Presentation	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations and Basis of Presentation	Nature of Operations and Basis of Presentation Essent Group Ltd. (“Essent Group”) is a Bermuda-based holding company, which, through its wholly-owned subsidiaries, offers private mortgage insurance and reinsurance for mortgages secured by residential properties located in the United States. Mortgage insurance facilitates the sale of low down payment (generally less than 20%) mortgage loans into the secondary mortgage market, primarily to two government-sponsored enterprises ("GSEs"), Fannie Mae and Freddie Mac. The primary mortgage insurance operations are conducted through Essent Guaranty, Inc. ("Essent Guaranty"), which is domiciled in the state of Pennsylvania. Essent Guaranty is headquartered in Radnor, Pennsylvania and maintains operations centers in Winston-Salem, North Carolina and Irvine, California. Essent Guaranty is approved as a qualified mortgage insurer by the GSEs and is licensed to write mortgage insurance in all 50 states and the District of Columbia. Effective July 2014, Essent Guaranty began to reinsure 25% of GSE-eligible new insurance written to Essent Reinsurance Ltd. (“Essent Re”), an affiliated Bermuda domiciled Class 3A Insurer licensed pursuant to Section 4 of the Bermuda Insurance Act 1978 that provides insurance and reinsurance coverage of mortgage credit risk. Essent Re also provides insurance and reinsurance to Freddie Mac and Fannie Mae. In 2016, Essent Re formed Essent Agency (Bermuda) Ltd., a wholly-owned subsidiary, which provides underwriting services to third-party reinsurers. In accordance with certain state law requirements, Essent Guaranty also reinsures that portion of the risk that is in excess of 25% of the mortgage balance with respect to any loan insured, after consideration of other reinsurance, to Essent Guaranty of PA, Inc. (“Essent PA”), an affiliate domiciled in the state of Pennsylvania. In addition to offering mortgage insurance, we provide contract underwriting services on a limited basis through CUW Solutions, LLC ("CUW Solutions"), a Delaware limited liability company, that provides, among other things, mortgage contract underwriting services to lenders and mortgage insurance underwriting services to affiliates. CUW Solutions is headquartered in Radnor, Pennsylvania and it maintains operations centers in Winston-Salem, North Carolina and Irvine, California that are subleased from Essent Guaranty. The Company operates as a single segment for reporting purposes as substantially all business operations, assets and liabilities relate to the private mortgage insurance business and management reviews operating results for the Company as a whole to make operating decisions and assess performance. The consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles ("GAAP") and include the accounts of Essent Group and its consolidated subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Certain amounts in prior years have been reclassified to conform to the current year presentation.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Use of Estimates

The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates.

Investments Available for Sale

Investments available for sale include securities that we sell from time to time to provide liquidity and in response to changes in the market. Debt and equity securities classified as available for sale are reported at fair value with unrealized gains and losses on these securities reported in other comprehensive income, net of deferred income taxes. See Note 16 for a description of the valuation methods for investments available for sale.

We monitor our fixed maturities for unrealized losses that appear to be other-than-temporary. A fixed maturity security is considered to be other-than-temporarily impaired when the security's fair value is less than its amortized cost basis and 1) we intend to sell the security, 2) it is more likely than not that we will be required to sell the security before recovery of the security's amortized cost basis, or 3) we believe we will be unable to recover the entire amortized cost basis of the security (i.e., a credit loss has occurred). When we determine that a credit loss has been incurred, but we do not intend to sell the security and it is not more likely than not that we will be required to sell the security before recovery of the security's amortized cost basis, the portion of the other-than-temporary impairment that is credit related is recorded as a realized loss in the consolidated statements of comprehensive income, and the portion of the other-than-temporary impairment that is not credit related is included in other comprehensive income. For those fixed maturities for which an other-than-temporary impairment has occurred, we adjust the amortized cost basis of the security and record a realized loss in the consolidated statements of comprehensive income.

We recognize purchase premiums and discounts in interest income using the interest method over the term of the securities. Gains and losses on the sales of securities are recorded on the trade date and are determined using the specific identification method.

Short-term investments are defined as short-term, highly liquid investments, both readily convertible to cash and having maturities at acquisition of twelve months or less.

Long-Lived Assets

Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is calculated using the straight-line method over the estimated useful lives of the assets. Repairs and maintenance are charged to expense as incurred. Estimated useful lives are 5 years for furniture and fixtures and 2 to 3 years for equipment, computer hardware and purchased software. Certain costs associated with the acquisition or development of internal-use software are capitalized. Once the software is ready for its intended use, these costs are amortized on a straight-line basis over the software's expected useful life, which is generally 3 years. We amortize leasehold improvements over the shorter of the lives of the leases or estimated service lives of the leasehold improvements. The balances by type were as follows at December 31:



	2017					2016
(In thousands)	Cost		Accumulated Depreciation/ Amortization			Cost		Accumulated Depreciation/ Amortization
Furniture and fixtures	$	2,074	$	(1,592	)	$	2,042	$	(1,298	)
Office equipment	640		(602		)	625		(513		)
Computer hardware	6,837		(5,413		)	5,700		(4,260		)
Purchased software	35,710		(34,620		)	35,148		(33,304		)
Costs of internal-use software	7,965		(6,773		)	7,140		(6,075		)
Leasehold improvements	4,219		(1,466		)	4,007		(1,093		)
Total	$	57,445	$	(50,466	)	$	54,662	$	(46,543	)

Deferred Policy Acquisition Costs

We defer certain personnel costs and premium tax expense directly related to the successful acquisition of new insurance policies and amortize these costs over the period the related estimated gross profits are recognized in order to match costs and revenues. We do not defer any underwriting costs associated with our contract underwriting services. Costs related to the acquisition of mortgage insurance business are initially deferred and reported as deferred policy acquisition costs. Consistent with industry accounting practice, amortization of these costs for each underwriting year book of business is recognized in proportion to estimated gross profits. Estimated gross profits are composed of earned premium, interest income, losses and loss adjustment expenses. The deferred costs are adjusted as appropriate for policy cancellations to be consistent with our revenue recognition policy. We estimate the rate of amortization to reflect actual experience and any changes to persistency or loss development. Deferred policy acquisition costs are reviewed periodically to determine that they do not exceed recoverable amounts, after considering investment income. Policy acquisition costs deferred were $8.0 million, $7.7 million and $6.6 million for the years ended December 31, 2017, 2016 and 2015, respectively. Amortization of deferred policy acquisition costs totaled $6.0 million, $5.8 million and $4.7 million for the years ended December 31, 2017, 2016 and 2015, respectively, and was included in other underwriting and operating expenses on the consolidated statements of comprehensive income.

Insurance Premium Revenue Recognition

Mortgage guaranty insurance policies are contracts that are generally non-cancelable by the insurer, are renewable at a fixed price, and provide for payment of premium on a monthly, annual or single basis. Upon renewal, we are not able to re-underwrite or re-price our policies. Consistent with industry accounting practices, premiums written on a monthly basis are earned as coverage is provided. Monthly policies accounted for 86% of earned premium in 2017. Premiums written on an annual basis are amortized on a pro rata basis over the year of coverage. Primary mortgage insurance written on policies covering more than one year are referred to as single premium policies. A portion of the revenue from single premium policies is recognized in earned premium in the current period, and the remaining portion is deferred as unearned premium and earned over the expected life of the policy. If single premium policies related to insured loans are cancelled due to repayment by the borrower, and the premium is non-refundable, then the remaining unearned premium related to each cancelled policy is recognized as earned premium upon notification of the cancellation. The Company recorded $23.2 million and $36.9 million of earned premium related to policy cancellations for the years ended December 31, 2017 and 2016, respectively. Unearned premium represents the portion of premium written that is applicable to the estimated unexpired risk of insured loans. Rates used to determine the earning of single premium policies are estimates based on an analysis of the expiration of risk.

Reserve for Losses and Loss Adjustment Expenses

We establish reserves for losses based on our best estimate of ultimate claim costs for defaulted loans using the general principles contained in ASC No. 944, in accordance with industry practice. However, consistent with industry standards for mortgage insurers, we do not establish loss reserves for future claims on insured loans which are not currently in default. Loans are classified as in default when the borrower has missed two consecutive payments. Once we are notified that a borrower has defaulted, we will consider internal and third-party information and models, including the status of the loan as reported by its servicer and the type of loan product to determine the likelihood that a default will reach claim status. In addition, we will project the amount that we will pay if a default becomes a claim (referred to as "claim severity"). Based on this information, at each reporting date we determine our best estimate of loss reserves at a given point in time. Included in loss reserves are reserves for incurred but not reported ("IBNR") claims. IBNR reserves represent our estimated unpaid losses on loans that are in default, but have not yet been reported to us as delinquent by our customers. We will also establish reserves for associated loss adjustment expenses, consisting of the estimated cost of the claims administration process, including legal and other fees and expenses associated with administering the claims process. Establishing reserves is inherently subjective as it requires estimates that are susceptible to significant revision as more information becomes available. Our estimates of claim rates and claim sizes will be strongly influenced by prevailing economic conditions, such as the overall state of the economy, current rates or trends in unemployment, changes in housing values and/or interest rates, and our best judgments as to the future values or trends of these macroeconomic factors. Losses incurred are also generally affected by the characteristics of our insured loans, such as the loan amount, loan-to-value ratio, the percentage of coverage on the insured loan and the credit quality of the borrower.

Premium Deficiency Reserve

We are required to establish a premium deficiency reserve if the net present value of the expected future losses and expenses for a particular group of policies exceeds the net present value of expected future premium, anticipated investment income and existing reserves for that specified group of policies. We reassess our expectations for premium, losses and expenses of our mortgage insurance business periodically and update our premium deficiency analysis accordingly. As of December 31, 2017 and 2016, we concluded that no premium deficiency reserve was required to be recorded in the accompanying consolidated financial statements.

Derivative Instruments

Through June 30, 2016, insurance and certain reinsurance policies issued by Essent Re in connection with Freddie Mac's Agency Credit Insurance Structure ("ACIS") program were accounted for as derivatives under GAAP with the fair value of these policies reported as an asset or liability and changes in the fair value of these policies reported in earnings as a component of other income. During the quarter ended September 30, 2016, these contracts were amended and are accounted for as insurance contracts rather than as derivatives subsequent to their amendment. As of December 31, 2017 and 2016, the Company had no derivative instruments.

Stock-Based Compensation

We measure the cost of employee services received in exchange for awards of equity instruments at the grant date of the award using a fair value based method. Prior to our initial public offering, we estimated the fair value of each nonvested share grant on the date of grant based on management's best estimate using methods further described in Note 10 of our consolidated financial statements. Subsequent to our initial public offering, fair value is determined on the date of grant based on quoted market prices. We recognize compensation expense on nonvested shares over the vesting period of the award. We adopted ASU 2016-09 Improvements to Employee Share-Based Payment Accounting (Topic 718) on January 1, 2017 and recorded a charge of $0.1 million to retained earnings as of that date representing a cumulative-effect adjustment associated with our election to recognize forfeitures as they occur rather than on an estimated basis. In connection with the adoption of this ASU, beginning in 2017, excess tax benefits and tax deficiencies associated with share-based payments are recognized as income tax expense or benefit in the income statement and treated as discrete items in the reporting period. Through December 31, 2016, excess tax benefits were recognized in additional paid-in-capital.

Income Taxes

Deferred income tax assets and liabilities are determined using the asset and liability (or balance sheet) method. Under this method, we determine the net deferred tax asset or liability based on the tax effects of the temporary differences between the book and tax bases of the various assets and liabilities and give current recognition to changes in tax rates and laws. Changes in tax laws, rates, regulations and policies, or the final determination of tax audits or examinations, could materially affect our tax estimates. We evaluate the realizability of the deferred tax asset and recognize a valuation allowance if, based on the weight of all available positive and negative evidence, it is more likely than not that some portion or all of the deferred tax asset will not be realized. When evaluating the realizability of the deferred tax asset, we consider estimates of expected future taxable income, existing and projected book/tax differences, carryback and carryforward periods, tax planning strategies available, and the general and industry specific economic outlook. This realizability analysis is inherently subjective, as it requires management to forecast changes in the mortgage market, as well as the related impact on mortgage insurance, and the competitive and general economic environment in future periods. Changes in the estimate of deferred tax asset realizability, if applicable, are included in income tax expense on the consolidated statements of comprehensive income.

ASC No. 740 provides a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. In accordance with ASC No. 740, before a tax benefit can be recognized, a tax position is evaluated using a threshold that it is more likely than not that the tax position will be sustained upon examination. When evaluating the more-likely-than-not recognition threshold, ASC No. 740 provides that a company should presume the tax position will be examined by the appropriate taxing authority that has full knowledge of all relevant information. If the tax position meets the more-likely-than-not recognition threshold, it is initially and subsequently measured as the largest amount of benefit that is greater than 50% likely of being realized upon ultimate settlement.

As described in Note 12, we purchase non-interest-bearing United States Mortgage Guaranty Tax and Loss Bonds ("T&L Bonds") issued by the Treasury Department. These assets are carried at cost and are reported as prepaid federal income tax on the consolidated balance sheets.

It is our policy to classify interest and penalties as income tax expense.

Earnings per Share

Basic earnings per common share amounts are calculated based on income available to common stockholders and the weighted average number of common shares outstanding during the reporting period. Diluted earnings per common share amounts are calculated based on income available to common stockholders and the weighted average number of common and potential common shares outstanding during the reporting period. Potential common shares, composed of the incremental common shares issuable upon vesting of unvested common shares and common share units, are included in the earnings per share calculation to the extent that they are dilutive.

Recently Issued Accounting Standards

In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") ASU 2014-09, Revenue from Contracts with Customers (Topic 606). This update is intended to provide a consistent approach in recognizing revenue. In accordance with the new standard, recognition of revenue occurs when a customer obtains control of promised goods or services in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In addition, the new standard requires that reporting companies disclose the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. In July 2015, the FASB delayed the effective date for this update to interim and annual periods beginning after December 15, 2017. In December 2016, the FASB clarified that all contracts that are within the scope of Topic 944, Financial Services-Insurance, are excluded from the scope of ASU 2014-09. Accordingly, this update will not impact the recognition of revenue related to insurance premiums or investments, which represent a significant portion of our total revenues. The adoption of this ASU is not expected to have a material effect on the Company's consolidated operating results or financial position.

In January 2016, the FASB issued ASU 2016-01, Financial Instruments-Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. This update requires certain equity investments (except those accounted for under the equity method of accounting or result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income. An entity may choose to measure equity investments that do not have readily determinable fair values at cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. A qualitative assessment for impairment is required for equity investments without readily determinable fair values. This update also requires public entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes. In addition, an entity is required to evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale investment securities in combination with the entity’s other deferred tax assets. The provisions of this update are effective for interim and annual periods beginning after December 15, 2017. The adoption of this ASU is not expected to have a material effect on the Company's consolidated operating results or financial position.

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). This update will require organizations that lease assets to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases. The new guidance will also require additional disclosures about the amount, timing and uncertainty of cash flows arising from leases. The provisions of this update are effective for annual and interim periods beginning after December 15, 2018. The Company expects a gross-up of its consolidated balance sheets as a result of recognizing lease liabilities and right of use assets. The Company is still evaluating the impact the adoption of this ASU will have on the consolidated financial statements.

In June 2016, the FASB issued ASU 2016-13, Measurement of Credit Losses on Financial Instruments (Topic 326). This update is intended to provide financial statement users with more information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. The amendments in this ASU replace the incurred loss impairment methodology in current GAAP with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. The new guidance requires financial assets measured at amortized cost to be presented at the net amount expected to be collected through the use of an allowance for credit losses. Credit losses relating to available-for-sale debt securities will also be recorded through an allowance rather than as a write-down of the amortized cost of the securities. The provisions of this update are effective for annual and interim periods beginning after December 15, 2019. While the Company is still evaluating this ASU, we do not expect it to impact our accounting for insurance losses and loss adjustment expenses ("LAE") as these items are not within the scope of this ASU.

In February 2018, the FASB issued ASU 2018-02, Income Statement- Reporting Comprehensive Income (Topic 220). This update permits entities to elect to reclassify the income tax effects of the Tax Cuts and Jobs Act (“TCJA”) on items within accumulated other comprehensive income to retained earnings. The provisions of this update are effective for annual and interim periods beginning after December 15, 2018 and early adoption is permitted. The Company adopted this ASU retrospective to 2017 and elected to reclassify the income tax effects of TCJA, totaling $0.9 million, from accumulated other comprehensive income to retained earnings. It is the Company’s policy to use the portfolio approach to release income tax effects from accumulated other comprehensive income.

Investments Available for Sale

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Investments Available for Sale

Investments available for sale consist of the following:



December 31, 2017 (In thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
U.S. Treasury securities	$	231,905	$	2	$	(4,102	)	$	227,805
U.S. agency securities	33,669		—		(555		)	33,114
U.S. agency mortgage-backed securities	462,986		567		(7,516		)	456,037
Municipal debt securities(1)	457,418		9,098		(1,261		)	465,255
Corporate debt securities(2)	610,516		4,249		(3,037		)	611,728
Residential and commercial mortgage securities	78,974		791		(358		)	79,407
Asset-backed securities	167,638		467		(183		)	167,922
Money market funds	263,808		—		(11		)	263,797
Total investments available for sale	$	2,306,914	$	15,174	$	(17,023	)	$	2,305,065



December 31, 2016 (In thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
U.S. Treasury securities	$	195,990	$	55	$	(4,497	)	$	191,548
U.S. agency securities	18,785		—		(344		)	18,441
U.S. agency mortgage-backed securities	324,654		335		(8,495		)	316,494
Municipal debt securities(1)	334,048		3,649		(3,373		)	334,324
Corporate debt securities(2)	457,842		2,343		(3,828		)	456,357
Residential and commercial mortgage securities	68,430		488		(582		)	68,336
Asset-backed securities	127,359		260		(447		)	127,172
Money market funds	102,430		—		—			102,430
Total investments available for sale	$	1,629,538	$	7,130	$	(21,566	)	$	1,615,102

_______________________________________________________________________________



	December 31,		December 31,
(1) The following table summarizes municipal debt securities as of :	2017		2016
Special revenue bonds	63.6	%	63.6	%
General obligation bonds	30.7		29.7
Certificate of participation bonds	4.4		4.9
Tax allocation bonds	0.8		1.1
Special tax bonds	0.5		0.7
Total	100.0	%	100.0	%



	December 31,		December 31,
(2) The following table summarizes corporate debt securities as of :	2017		2016
Financial	45.9	%	40.6	%
Consumer, non-cyclical	16.2		18.6
Energy	7.8		9.3
Communications	7.3		6.0
Industrial	6.3		5.6
Consumer, cyclical	5.3		6.3
Utilities	5.3		6.0
Technology	3.9		4.3
Basic materials	2.0		3.3
Total	100.0	%	100.0	%

The amortized cost and fair value of investments available for sale at December 31, 2017, by contractual maturity, are shown below. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Because most U.S. agency mortgage-backed securities, residential and commercial mortgage securities and asset-backed securities provide for periodic payments throughout their lives, they are listed below in separate categories.



(In thousands)	Amortized Cost		Fair Value
U.S. Treasury securities:
Due in 1 year	$	58,429	$	58,411
Due after 1 but within 5 years	72,469		71,661
Due after 5 but within 10 years	71,006		68,376
Due after 10 years	30,001		29,357
Subtotal	231,905		227,805
U.S. agency securities:
Due in 1 year	—		—
Due after 1 but within 5 years	33,669		33,114
Subtotal	33,669		33,114
Municipal debt securities:
Due in 1 year	33,038		32,998
Due after 1 but within 5 years	97,637		97,831
Due after 5 but within 10 years	179,245		183,610
Due after 10 years	147,498		150,816
Subtotal	457,418		465,255
Corporate debt securities:
Due in 1 year	80,177		80,093
Due after 1 but within 5 years	332,105		331,790
Due after 5 but within 10 years	196,289		197,848
Due after 10 years	1,945		1,997
Subtotal	610,516		611,728
U.S. agency mortgage-backed securities	462,986		456,037
Residential and commercial mortgage securities	78,974		79,407
Asset-backed securities	167,638		167,922
Money market funds	263,808		263,797
Total investments available for sale	$	2,306,914	$	2,305,065

Gross gains and losses realized on the sale of investments available for sale were as follows:



	Year Ended December 31,
(In thousands)	2017		2016		2015
Realized gross gains	$	2,504	$	2,822	$	3,908
Realized gross losses	425		788		1,073

The fair value of investments in an unrealized loss position and the related unrealized losses were as follows:



	Less than 12 months					12 months or more					Total
December 31, 2017 (In thousands)	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
U.S. Treasury securities	$	151,119	$	(1,240	)	$	69,454	$	(2,862	)	$	220,573	$	(4,102	)
U.S. agency securities	17,320		(190		)	15,794		(365		)	33,114		(555		)
U.S. agency mortgage-backed securities	180,443		(1,394		)	217,944		(6,122		)	398,387		(7,516		)
Municipal debt securities	124,171		(817		)	23,492		(444		)	147,663		(1,261		)
Corporate debt securities	214,371		(1,213		)	94,261		(1,824		)	308,632		(3,037		)
Residential and commercial mortgage securities	29,842		(179		)	5,988		(179		)	35,830		(358		)
Asset-backed securities	58,798		(133		)	5,828		(50		)	64,626		(183		)
Money market funds	59,489		(11		)	—		—			59,489		(11		)
Total	$	835,553	$	(5,177	)	$	432,761	$	(11,846	)	$	1,268,314	$	(17,023	)



	Less than 12 months					12 months or more					Total
December 31, 2016 (In thousands)	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
U.S. Treasury securities	$	160,018	$	(4,497	)	$	—	$	—		$	160,018	$	(4,497	)
U.S. agency securities	18,441		(344		)	—		—			18,441		(344		)
U.S. agency mortgage-backed securities	289,282		(8,402		)	1,812		(93		)	291,094		(8,495		)
Municipal debt securities	149,368		(3,351		)	6,015		(22		)	155,383		(3,373		)
Corporate debt securities	213,965		(3,704		)	8,344		(124		)	222,309		(3,828		)
Residential and commercial mortgage securities	18,026		(434		)	14,014		(148		)	32,040		(582		)
Asset-backed securities	28,294		(57		)	47,597		(390		)	75,891		(447		)
Total	$	877,394	$	(20,789	)	$	77,782	$	(777	)	$	955,176	$	(21,566	)

The gross unrealized losses on these investment securities are principally associated with the changes in market interest rates and credit spreads subsequent to their purchase. Each issuer is current on its scheduled interest and principal payments. We assess our intent to sell these securities and whether we will be required to sell these securities before the recovery of their amortized cost basis when determining whether an impairment is other-than-temporary. We recorded other-than-temporary impairments of $0.1 million, $0.1 million and $0.3 million in the years ended December 31, 2017, 2016 and 2015, respectively, on securities in an unrealized loss position. The impairments resulted from our intent to sell these securities subsequent to the reporting dates.

The fair value of investments deposited with insurance regulatory authorities to meet statutory requirements was $8.6 million at December 31, 2017 and $8.5 million at December 31, 2016. In connection with its insurance and reinsurance activities, Essent Re is required to maintain assets in trusts for the benefit of its contractual counterparties. The fair value of the investments on deposit in these trusts was $615.8 million at December 31, 2017 and $349.6 million at December 31, 2016.

Net investment income consists of:



	Year Ended December 31,
(In thousands)	2017			2016			2015
Fixed maturities	$	41,935		$	29,865		$	21,693
Short-term investments	1,019			142			63
Gross investment income	42,954			30,007			21,756
Investment expenses	(2,728		)	(2,117		)	(1,871		)
Net investment income	$	40,226		$	27,890		$	19,885

Accounts Receivable

12 Months Ended

Dec. 31, 2017

Receivables [Abstract]

Accounts Receivable

Accounts receivable consists of the following at December 31:



(In thousands)	2017		2016
Premiums receivable	$	29,027	$	21,265
Other receivables	725		367
Total accounts receivable	29,752		21,632
Less: Allowance for doubtful accounts	—		—
Accounts receivable, net	$	29,752	$	21,632

Premiums receivable consists of premiums due on our mortgage insurance policies. If mortgage insurance premiums are unpaid for more than 90 days, the receivable is written off against earned premium and the related insurance policy is cancelled. For all periods presented, no provision or allowance for doubtful accounts was required.

- Definition

The entire disclosure for claims held for amounts due a entity, excluding financing receivables. Examples include, but are not limited to, trade accounts receivables, notes receivables, loans receivables. Includes disclosure for allowance for credit losses.

+ References + Details

Triad Transaction	12 Months Ended
Triad Transaction	Dec. 31, 2017
Business Combinations [Abstract]
Triad Transaction	Triad Transaction On December 1, 2009, under the terms of an asset purchase agreement (the "Asset Purchase Agreement") dated October 7, 2009 between Essent Guaranty and Triad Guaranty, Inc. and Triad Guaranty Insurance Corporation (collectively referred to as "Triad"), we acquired all of Triad's proprietary mortgage insurance information technology and operating platform, certain software and substantially all of the supporting hardware, as well as furniture and fixtures, in exchange for fixed payments of $15 million, contingent payments of $15 million, and the assumption of certain contractual obligations. The final contingent payment was made in the year ended December 31, 2014 and no further amounts are due to Triad under the Asset Purchase Agreement. Effective with the completion of the transaction, Essent Guaranty began providing information systems maintenance and development services, customer service and policy administration support to Triad under the terms of a services agreement dated December 1, 2009. Triad retains the obligation for all risks insured under its existing insurance contracts and will continue to directly manage loss mitigation and claim activity on its insured business. Under the terms of the services agreement, we provide the following services to Triad in exchange for fees: (i) maintain and support the licensed technology and equipment and provide to Triad certain information and technology services; (ii) access to the Triad technology platform in order to support Triad's business pursuant to the license grant outlined in the services agreement; (iii) customer support-related services; and (iv) technology development services. Effective December 1, 2010, the fee is based principally on the number of Triad's insurance policies in force on a monthly basis. Accordingly, this fee is reduced as Triad's policies in force decline. We earned fees under the services agreement of $1.1 million, $1.4 million and $1.8 million for the years ended December 31, 2017, 2016 and 2015, respectively, which are included in other income in the accompanying consolidated statements of comprehensive income.

Reserve for Losses and Loss Adjustment Expenses

12 Months Ended

Dec. 31, 2017

Liability for Future Policy Benefits and Unpaid Claims and Claims Adjustment Expense [Abstract]

Reserve for Losses and Loss Adjustment Expenses

The following table provides a reconciliation of the beginning and ending reserve balances for losses and loss adjustment expenses ("LAE") for the years ended December 31:



($ in thousands)	2017			2016
Reserve for losses and LAE at beginning of year	$	28,142		$	17,760
Less: Reinsurance recoverables	—			—
Net reserve for losses and LAE at beginning of year	28,142			17,760
Add provision for losses and LAE, net of reinsurance, occurring in:
Current year	38,178			21,889
Prior years	(10,946		)	(6,364		)
Net incurred losses during the current year	27,232			15,525
Deduct payments for losses and LAE, net of reinsurance, occurring in:
Current year	633			927
Prior years	7,891			4,216
Net loss and LAE payments during the current year	8,524			5,143
Net reserve for losses and LAE at end of year	46,850			28,142
Plus: Reinsurance recoverables	—			—
Reserve for losses and LAE at end of year	$	46,850		$	28,142

Loans in default at end of year	4,783			1,757

For the year ended December 31, 2017, $7.9 million was paid for incurred claims and claim adjustment expenses attributable to insured events of prior years. There has been a $10.9 million favorable prior year development during the year ended December 31, 2017. Reserves remaining as of December 31, 2017 for prior years are $9.3 million as a result of re-estimation of unpaid losses and loss adjustment expenses. For the year ended December 31, 2016, $4.2 million was paid for incurred claims and claim adjustment expenses attributable to insured events of prior years. There was a $6.4 million favorable prior year development during the year ended December 31, 2016. Reserves remaining as of December 31, 2016 for prior years were $7.2 million as a result of re-estimation of unpaid losses and loss adjustment expenses. In both periods, the favorable prior years' loss development was the result of a re-estimation of amounts ultimately to be paid on prior year defaults in the default inventory, including the impact of previously identified defaults that cured. Original estimates are increased or decreased as additional information becomes known regarding individual claims.

During the third quarter of 2017, certain regions of the U.S. experienced hurricanes which have impacted our insured portfolio’s performance. Specifically, on August 26, 2017, Hurricane Harvey made landfall in southeastern Texas and on September 10, 2017, Hurricane Irma made landfall in southern Florida and caused property damage in certain counties. Loans in default increased by 3,026 in the year ended December 31, 2017, including 2,288 defaults we identified as hurricane-related defaults. Based on prior industry experience, we expect the ultimate number of hurricane-related defaults that result in claims will be less than the default-to-claim experience of non-hurricane-related defaults. In addition, under our master policy, our exposure may be limited on hurricane-related claims. For example, we are permitted to exclude a claim entirely where damage to the property underlying a mortgage was the proximate cause of the default and adjust a claim where the property underlying a mortgage in default is subject to unrestored physical damage. Accordingly, when establishing our loss reserves as of December 31, 2017, we applied a lower estimated claim rate to new default notices received in the fourth quarter of 2017 from the affected areas than the claim rate we apply to other notices in our default inventory. The reserve for losses and LAE on hurricane-related defaults was $11.1 million at December 31, 2017. The impact on our reserves in future periods will be dependent upon the performance of the hurricane-related defaults and our expectations for the amount of ultimate losses on these delinquencies.

The following table summarizes incurred loss and allocated loss adjustment expense development, IBNR plus expected development on reported defaults and the cumulative number of reported defaults. The information about incurred loss development for the years ended December 31, 2010 to 2016 is presented as supplementary information.



($ in thousands)	Incurred Loss and Allocated LAE, For the Years Ended December 31,																As of December 31, 2017
Accident Year	2010 Unaudited		2011 Unaudited		2012 Unaudited		2013 Unaudited		2014 Unaudited		2015 Unaudited		2016 Unaudited		2017		Total of IBNR plus Expected Development on Reported Defaults		Cumulative Number of Reported Defaults (1)
2010	$	—	$	—	$	—	$	—	$	—	$	—	$	—	$	—	$	—	—
2011			57		—		—		—		—		—		—		—		1
2012					1,523		858		814		781		748		809		—		19
2013							2,986		2,461		2,008		1,997		2,060		12		52
2014									6,877		4,312		3,323		2,984		14		98
2015											14,956		9,625		8,893		134		238
2016													21,889		11,890		482		388
2017															38,178		2,573		4,494
Total															$	64,814

(1) Cumulative number of reported defaults includes cumulative paid claims plus loans in default by accident year as of December 31, 2017.

The following table summarizes cumulative paid losses and allocated loss adjustment expenses, net of reinsurance. The information about paid loss development for the years ended December 31, 2010 through 2016 is presented as supplementary information.



($ in thousands)	Cumulative Paid Losses and Allocated LAE For the Years Ended December 31,
Accident Year	2010 Unaudited		2011 Unaudited		2012 Unaudited		2013 Unaudited		2014 Unaudited		2015 Unaudited		2016 Unaudited		2017
2010	$	—	$	—	$	—	$	—	$	—	$	—	$	—	—
2011			—		—		—		—		—		—		—
2012					24		535		659		665		665		808
2013							239		928		1,501		1,775		1,880
2014									138		1,587		2,463		2,787
2015											544		3,610		6,960
2016													927		4,896
2017															633
Total															$	17,964
All outstanding liabilities before 2010, net of reinsurance															—
Reserve for losses and LAE, net of reinsurance															$	46,850

For our mortgage insurance portfolio, our average annual payout of losses as of December 31, 2017 is as follows:



Average Annual Percentage Payout of Incurred Losses and Allocated LAE by Year
Year	1		2		3		4		5		6

Average Payout	6	%	43	%	28	%	8	%	3	%	18	%

Debt Obligations	12 Months Ended
Debt Obligations	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt Obligations	Debt Obligations Credit Facility On May 17, 2017, Essent Group and its subsidiaries, Essent Irish Intermediate Holdings Limited and Essent US Holdings, Inc. (collectively, the "Borrowers"), entered into an amended and restated four-year, secured credit facility with a committed capacity of $375 million (the “Credit Facility”). The Credit Facility amends and restates the three-year, secured revolving credit facility entered into on April 19, 2016, and provides for (i) an increase in the revolving credit facility from $200 million to $250 million, (ii) the issuance of term loans of $125 million, the proceeds of which were used at closing to pay down borrowings outstanding under the revolving credit facility, and (iii) a $75 million uncommitted line that may be exercised at the Borrowers’ option so long as the Borrowers receive commitments from the lenders. Borrowings under the Credit Facility may be used for working capital and general corporate purposes, including, without limitation, capital contributions to Essent’s insurance and reinsurance subsidiaries. Borrowings will accrue interest at a floating rate tied to a standard short-term borrowing index, selected at the Company’s option, plus an applicable margin. A commitment fee is due quarterly on the average daily amount of the undrawn revolving commitment. The applicable margin and the commitment fee are based on the senior unsecured debt rating or long-term issuer rating of Essent Group to the extent available, or the insurer financial strength rating of Essent Guaranty. The current annual commitment fee rate is 0.35%. The obligations under the Credit Facility are secured by certain assets of the Borrowers, excluding the stock and assets of its insurance and reinsurance subsidiaries. The Credit Facility contains several covenants, including financial covenants relating to minimum net worth, capital and liquidity levels, maximum debt to capitalization level and Essent Guaranty's compliance with the PMIERs (see Note 17). The $125 million term loans contractually mature on May 17, 2021. This description is not intended to be complete in all respects and is qualified in its entirety by the terms of the Credit Facility, including its covenants. As of December 31, 2017, the Company was in compliance with the covenants and $250 million had been borrowed under the Credit Facility with a weighted average interest rate of 3.49%. As of December 31, 2016, $100 million had been borrowed with a weighted average interest rate of 2.73%.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Obligations under Guarantees

Under the terms of CUW Solutions' contract underwriting agreements with lenders and subject to contractual limitations on liability, we agree to indemnify certain lenders against losses incurred in the event that we make an error in determining whether loans processed meet specified underwriting criteria, to the extent that such error materially restricts or impairs the salability of such loan, results in a material reduction in the value of such loan or results in the lender repurchasing the loan. The indemnification may be in the form of monetary or other remedies. For the years ended December 31, 2017 and 2016, we paid $0.2 million and $0.1 million, respectively, related to remedies. As of December 31, 2017, management believes any potential claims for indemnification related to contract underwriting services through December 31, 2017 are not material to our consolidated financial position or results of operations.

In addition to the indemnifications discussed above, in the normal course of business, we enter into agreements or other relationships with third parties pursuant to which we may be obligated under specified circumstances to indemnify the counterparties with respect to certain matters. Our contractual indemnification obligations typically arise in the context of agreements entered into by us to, among other things, purchase or sell services, finance our business and business transactions, lease real property and license intellectual property. The agreements we enter into in the normal course of business generally require us to pay certain amounts to the other party associated with claims or losses if they result from our breach of the agreement, including the inaccuracy of representations or warranties. The agreements we enter into may also contain other indemnification provisions that obligate us to pay amounts upon the occurrence of certain events, such as the negligence or willful misconduct of our employees, infringement of third-party intellectual property rights or claims that performance of the agreement constitutes a violation of law. Generally, payment by us under an indemnification provision is conditioned upon the other party making a claim, and typically we can challenge the other party's claims. Further, our indemnification obligations may be limited in time and/or amount, and in some instances, we may have recourse against third parties for certain payments made by us under an indemnification agreement or obligation. As of December 31, 2017, contingencies triggering material indemnification obligations or payments have not occurred historically and are not expected to occur. The nature of the indemnification provisions in the various types of agreements and relationships described above are believed to be low risk and pervasive, and we consider them to have a remote risk of loss or payment. We have not recorded any provisions on the consolidated balance sheets related to these indemnifications.

Commitments

We lease office space for use in our operations under leases accounted for as operating leases. Total rent expense was $2.1 million, $1.9 million and $1.9 million for the years ended December 31, 2017, 2016 and 2015, respectively. The future minimum lease payments of non-cancelable operating leases are as follows at December 31, 2017:



Year Ended December 31 (In thousands)
2018	$	2,479
2019	2,649
2020	2,594
2021	2,651
2022	2,710
2023 and thereafter	4,517
Total minimum payments required	$	17,600

Minimum lease payments shown above have not been reduced by minimum sublease rental income of $0.1 million due in 2018 under the non-cancelable sublease.

Capital Stock	12 Months Ended
Capital Stock	Dec. 31, 2017
Capital [Abstract]
Capital Stock	Capital Stock Our authorized share capital consists of 233.3 million shares of a single class of common shares (the "Common Shares"). The Common Shares have no pre-emptive rights or other rights to subscribe for additional shares, and no rights of redemption, conversion or exchange. Under certain circumstances and subject to the provisions of Bermuda law and our bye-laws, we may be required to make an offer to repurchase shares held by members. The Common Shares rank pari passu with one another in all respects as to rights of payment and distribution. In general, holders of Common Shares will have one vote for each Common Share held by them and will be entitled to vote, on a non-cumulative basis, at all meetings of shareholders. In the event that a shareholder is considered a 9.5% Shareholder under our bye-laws, such shareholder's votes will be reduced by whatever amount is necessary so that after any such reduction the votes of such shareholder will not result in any other person being treated as a 9.5% Shareholder with respect to the vote on such matter. Under these provisions certain shareholders may have their voting rights limited to less than one vote per share, while other shareholders may have voting rights in excess of one vote per share. In August 2017, Essent Group completed the sale of 5.0 million Common Shares in a public offering at a price of $39.90 per share. The total net proceeds from this offering were approximately $197.7 million after deducting underwriting discounts, commissions and other offering expenses.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-Based Compensation

In connection with the IPO in 2013, Essent Group's Board of Directors adopted, and Essent Group's shareholders approved, the Essent Group Ltd. 2013 Long-Term Incentive Plan (the "2013 Plan"), which was effective upon completion of the initial public offering. The types of awards available under the 2013 Plan include nonvested shares, nonvested share units, non-qualified share options, incentive stock options, share appreciation rights, and other share-based or cash-based awards. Amendments to our 2013 Plan were approved by shareholders and effective as of May 3, 2017. These amendments included a reduction in the maximum number of shares and share units available for issuance to 7.5 million under the Amended and Restated 2013 Plan (inclusive of approximately 2.6 million nonvested shares and share units outstanding as of May 3, 2017), down from the approximately 14.7 million shares and share units originally available for issuance under the 2013 Plan. As of December 31, 2017, there were 4.9 million Common Shares available for future grant under the 2013 Plan.

In September 2013 and February 2014, certain members of senior management were granted nonvested Common Shares under the 2013 Plan that were subject to time-based and performance-based vesting. The time-based share awards granted in September 2013 vest in four equal installments on January 1, 2015, 2016, 2017 and 2018. The time-based share awards granted in February 2014 vested in three equal installments on March 1, 2015, 2016 and 2017. The performance-based share awards vest based upon our compounded annual book value per share growth percentage during a three-year performance period that commenced on January 1, 2014. The September 2013 performance-based share awards vest on the one-year anniversary of the completion of the performance period, and the February 2014 performance-based share awards vested on March 1, 2017.

In February 2015, certain members of senior management were granted nonvested Common Shares under the 2013 Plan that were subject to time-based and performance-based vesting. The time-based share awards granted in February 2015 vest in three equal installments on March 1, 2016, 2017 and 2018. The performance-based share awards granted in February 2015 vest based upon our compounded annual book value per share growth percentage during a three-year performance period that commenced on January 1, 2015 and vest on March 1, 2018.

In May 2015, nonvested Common Shares were granted to an employee in connection with an employment agreement that are subject to time-based and performance-based vesting. The time-based share award vests in four equal installments on July 1, 2016, 2017, 2018 and 2019. The performance-based share award vests based upon our compounded annual book value per share growth percentage during a three-year performance period that commenced on January 1, 2015 and vests on July 1, 2019.

In February 2016, certain members of senior management were granted nonvested common shares under the 2013 Plan that are subject to time-based and performance-based vesting. The time-based share awards granted in February 2016 vest in three equal installments on March 1, 2017, 2018 and 2019. The performance-based share awards granted in February 2016 vest based upon our compounded annual book value per share growth percentage during a three-year performance period that commenced on January 1, 2016 and vest on March 1, 2019.

In February 2017, certain members of senior management were granted nonvested common shares under the 2013 Plan that were subject to time-based and performance-based vesting. The time-based share awards granted in February 2017 vest in three equal installments on March 1, 2018, 2019 and 2020. The performance-based share awards granted in February 2017 vest based upon our compounded annual book value per share growth percentage during a three-year performance period that commenced on January 1, 2017 and vest on March 1, 2020.

The portion of the nonvested performance-based share awards that will be earned based upon the achievement of compounded annual book value per share growth is as follows:



	2017 Performance-Based Grants				2016 Performance-Based Grants				2013, 2014 and 2015 Performance-Based Grants
Performance level	Compounded Annual Book Value Per Share Growth		Nonvested Common Shares Earned		Compounded Annual Book Value Per Share Growth		Nonvested Common Shares Earned		Compounded Annual Book Value Per Share Growth		Nonvested Common Shares Earned
	<16	%	0	%	<13	%	0	%	<11	%	0	%
Threshold	16	%	25	%	13	%	25	%	11	%	10	%
	17	%	50	%	14	%	50	%	12	%	36	%
	18	%	75	%	15	%	75	%	13	%	61	%
									14	%	87	%
Maximum	≥19	%	100	%	≥16	%	100	%	≥15	%	100	%

In the event that the compounded annual book value per share growth falls between the performance levels shown above, the nonvested Common Shares earned will be determined on a straight-line basis between the respective levels shown. The compounded annual book value per share growth for each of the 2013, 2014 and 2015 performance-based grants exceeded the maximum performance level and have vested or will vest at 100%.

In connection with our incentive program covering bonus awards for performance year 2013, in February 2014, time-based share awards and share units were issued to certain employees that vested in three equal installments on January 1, 2015, 2016 and 2017. In connection with our incentive program covering bonus awards for performance year 2014, in February 2015, time-based share awards and share units were issued to certain employees that vest in three equal installments on March 1, 2016, 2017 and 2018. In connection with our incentive program covering bonus awards for performance year 2015, in February 2016, time-based share awards and share units were issued to certain employees that vest in three equal installments on March 1, 2017, 2018 and 2019. In January 2017, time-based share units were issued to all vice president and staff level employees that vest in three equal installments in January 2018, 2019 and 2020. In connection with our incentive program covering bonus awards for performance year 2016, in February 2017, time-based share awards and share units were issued to certain employees that vest in three equal installments on March 1, 2018, 2019 and 2020.

In May of each year, 2015 through 2017, time-based share units were granted to non-employee directors that vest one year from the date of grant.

The following tables summarize nonvested Common Share and nonvested Common Share unit activity for the year ended December 31:



	2017
	Time and Performance- Based Share Awards				Time-Based Share Awards				Share Units
(Shares in thousands)	Number of Shares		Weighted Average Grant Date Fair Value		Number of Shares		Weighted Average Grant Date Fair Value		Number of Share Units		Weighted Average Grant Date Fair Value
Outstanding at beginning of year	1,503		$	15.41	605		$	16.32	493		$	19.24
Granted	140		36.29		91		36.29		387		33.40
Vested	(48	)	22.48		(286	)	15.74		(321	)	19.00
Forfeited	—		N/A		—		N/A		(23	)	30.49
Outstanding at end of year	1,595		$	17.03	410		$	21.12	536		$	29.13



	2016
	Time and Performance- Based Share Awards			Time-Based Share Awards				Share Units
(Shares in thousands)	Number of Shares	Weighted Average Grant Date Fair Value		Number of Shares		Weighted Average Grant Date Fair Value		Number of Share Units		Weighted Average Grant Date Fair Value
Outstanding at beginning of year	1,294	$	15.15	890		$	12.31	544		$	19.84
Granted	209	17.01		181		17.01		215		18.21
Vested	—	N/A		(461	)	9.04		(254	)	19.71
Forfeited	—	N/A		(5	)	0.23		(12	)	18.12
Outstanding at end of year	1,503	$	15.41	605		$	16.32	493		$	19.24



	2015
	Time and Performance- Based Share Awards				Time-Based Share Awards				Share Units
(Shares in thousands)	Number of Shares		Weighted Average Grant Date Fair Value		Number of Shares		Weighted Average Grant Date Fair Value		Number of Share Units		Weighted Average Grant Date Fair Value
Outstanding at beginning of year	1,290		$	14.83	1,472		$	9.04	664		$	18.32
Granted	50		24.58		109		24.51		129		24.47
Vested	—		N/A		(644	)	6.67		(239	)	18.18
Forfeited	(46	)	16.40		(47	)	15.50		(10	)	17.89
Outstanding at end of year	1,294		$	15.15	890		$	12.31	544		$	19.84

Quoted market prices are used for the valuation of Common Shares granted subsequent to our initial public offering. For nonvested Common Shares granted in September 2013, prior to our IPO, the valuation estimate was based on analysis provided by the underwriters regarding the estimated fair value of Essent and the estimated IPO price range. Factors considered in determining the IPO price range and Common Share valuation included prevailing market conditions, estimates of the Company's business potential and earnings prospects, the Company's historical operating results, market valuations of companies deemed comparable to the Company and an assessment of risks and opportunities.

The total fair value of nonvested shares or share units that vested was $22.4 million, $15.6 million and $22.4 million for the years ended December 31, 2017, 2016 and 2015, respectively. As of December 31, 2017, there was $18.4 million of total unrecognized compensation expense related to nonvested shares or share units outstanding at December 31, 2017 and we expect to recognize the expense over a weighted average period of 1.8 years.

In connection with our incentive program covering bonus awards for performance year 2017, in February 2018, 90,283 nonvested Common Share units were issued to certain employees and are subject to time-based vesting. In February 2018, 185,896 nonvested Common Shares were granted to certain members of senior management and are subject to time-based and performance-based vesting.

Employees have the option to tender shares to Essent Group to pay the minimum employee statutory withholding taxes associated with shares upon vesting. Common Shares tendered by employees to pay employee withholding taxes totaled 223,027, 184,583 and 201,553 in 2017, 2016 and 2015, respectively. The tendered shares were recorded at cost and included in treasury stock. All treasury stock has been cancelled as of December 31, 2017 and 2016.

Compensation expense, net of forfeitures, and related tax effects recognized in connection with nonvested shares were as follows for the years ended December 31:



(In thousands)	2017		2016		2015
Compensation expense	$	18,688	$	16,881	$	13,633
Income tax benefit	6,017		5,455		4,378

Dividends Restrictions	12 Months Ended
Dividends Restrictions	Dec. 31, 2017
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments [Abstract]
Dividends Restrictions	Dividends Restrictions Our U.S. insurance subsidiaries are subject to certain capital and dividend rules and regulations as prescribed by jurisdictions in which they are authorized to operate. Under the insurance laws of the Commonwealth of Pennsylvania, Essent Guaranty and Essent PA may pay dividends during any 12-month period in an amount equal to the greater of (i) 10% of the preceding year-end statutory policyholders' surplus or (ii) the preceding year's statutory net income. The Pennsylvania statute also specifies that dividends and other distributions can be paid out of positive unassigned surplus without prior approval. At December 31, 2017, Essent Guaranty had unassigned surplus of approximately $70.7 million. Essent Guaranty paid no dividends to Essent Group or any intermediate holding companies in the years ended December 31, 2017, 2016 or 2015. Essent PA had unassigned surplus of approximately $6.5 million as of December 31, 2017. In the years ended December 31, 2017 and 2016, Essent PA paid to its parent company, Essent US Holdings, Inc. ("Essent Holdings") a dividend of $5 million and $3.75 million, respectively. Essent PA did not pay a dividend in 2015. Essent Re is subject to certain dividend restrictions as prescribed by the Bermuda Monetary Authority and under certain agreements with counterparties. In connection with the quota share reinsurance agreement with Essent Guaranty, Essent Re has agreed to maintain a minimum total equity of $100 million. As of December 31, 2017, Essent Re had total equity of $662.8 million. At December 31, 2017, our insurance subsidiaries were in compliance with these rules, regulations and agreements.

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Income Taxes

Through December 31, 2017, the statutory income tax rates of the countries where the Company does business are 35% in the United States and 0.0% in Bermuda. The statutory income tax rate of each country is applied against the taxable income from each country to calculate the income tax expense. On December 22, 2017, the “Tax Cuts and Jobs Act” (“TCJA”) was enacted. The provisions of TCJA include broad tax reforms that are applicable to the Company, including a reduction in the U.S. statutory corporate income tax rate from 35% to 21% effective January 1, 2018. This change in tax rates required us to remeasure our deferred tax assets and liabilities as of the enactment date resulting in a one-time $85.1 million income tax benefit for the year ended December 31, 2017.

Income tax expense consists of the following components for the years ended December 31:



(In thousands)	2017			2016		2015
Current	$	38,252		$	31,712	$	18,910
Deferred	65,660			57,564		52,157
Remeasurement of net deferred tax liability for enacted changes in tax law	(85,091		)	—		—
Total income tax expense	$	18,821		$	89,276	$	71,067

For the year ended December 31, 2017 pre-tax income attributable to Bermuda and U.S. operations was $86.3 million and $312.3 million, respectively, as compared to $51.6 million and $260.3 million, respectively, for the year ended December 31, 2016 and $21.4 million and $207.0 million, respectively, for the year ended December 31, 2015.

Income tax expense is different from that which would be obtained by applying the applicable statutory income tax rates to income before taxes by jurisdiction (i.e. U.S. 35%; Bermuda 0.0%). The reconciliation of the difference between income tax expense and the expected tax provision at the weighted average tax rate was as follows for the years ended December 31:



($ in thousands)	2017			% of pretax income		2016			% of pretax income		2015			% of pretax income
Tax provision at weighted average statutory rates	$	109,309		27.4	%	$	91,092		29.2	%	$	72,461		31.7	%
Change in valuation of net deferred tax liability	(85,091		)	(21.3	)	—			—		—			—
Excess tax benefits from stock-based compensation	(3,227		)	(0.8	)	—			—		—			—
Tax exempt interest, net of proration	(2,608		)	(0.7	)	(2,181		)	(0.7	)	(1,741		)	(0.8	)
Non-deductible expenses	392			0.1		378			0.1		381			0.2
Other	46			0.0		(13		)	0.0		(34		)	0.0
Total income tax expense	$	18,821		4.7	%	$	89,276		28.6	%	$	71,067		31.1	%

We provide deferred taxes to reflect the estimated future tax effects of the differences between the financial statement and tax bases of assets and liabilities using currently enacted tax laws. The net deferred tax liability was comprised of the following at December 31:



(In thousands)	2017			2016
Deferred tax assets	$	28,696		$	43,291
Deferred tax liabilities	(156,332		)	(185,878		)
Net deferred tax liability	$	(127,636	)	$	(142,587	)

The components of the net deferred tax liability were as follows at December 31:



(In thousands)	2017			2016
Contingency reserves	$	(151,586	)	$	(181,031	)
Unearned premium reserve	14,454			19,722
Nonvested shares	6,442			8,445
Deferred policy acquisition costs	(3,224		)	(4,690		)
Unearned ceding commissions	2,815			3,568
Fixed assets	2,529			4,702
Start-up expenditures, net	1,951			3,705
Unrealized (gain) loss on investments	(1,403		)	2,181
Accrued expenses	335			775
Loss reserves	158			170
Prepaid expenses	(119		)	(157		)
Organizational expenditures	12			23
Net deferred tax liability	$	(127,636	)	$	(142,587	)

As a mortgage guaranty insurer, we are eligible for a tax deduction, subject to certain limitations, under Section 832(e) of the IRC for amounts required by state law or regulation to be set aside in statutory contingency reserves. The deduction is allowed only to the extent that we purchase T&L Bonds in an amount equal to the tax benefit derived from deducting any portion of our statutory contingency reserves. During the years ended December 31, 2017 and 2016, we had net purchases of T&L Bonds in the amount of $70.9 million and $61.9 million, respectively, and held $252.2 million and $181.3 million of T&L Bonds as of December 31, 2017 and 2016, respectively.

In evaluating our ability to realize the benefit of our deferred tax assets, we consider the relevant impact of all available positive and negative evidence including our past operating results and our forecasts of future taxable income. At December 31, 2017 and 2016, after weighing all the evidence, management concluded that it was more likely than not that our deferred tax assets would be realized.

Under current Bermuda law, the parent company, Essent Group, and its Bermuda subsidiary, Essent Re, are not required to pay any taxes on income and capital gains. In the event that there is a change such that these taxes are imposed, these companies would be exempted from any such tax until March of 2035 pursuant to the Bermuda Exempt Undertakings Tax Protection Act of 1966, and the Exempt Undertakings Tax Protection Amendment Act of 2011.

Essent Holdings and its subsidiaries are subject to income taxes imposed by U.S. law and file a U.S. Consolidated Income Tax Return. Each subsidiary has executed a tax sharing agreement with its parent company, which provides that taxes are settled in cash between parent and subsidiary on a quarterly basis based on separate company pro-forma calculations. Should Essent Holdings pay a dividend to its parent company, Essent Irish Intermediate Holdings Limited, withholding taxes at a rate of 5% under the U.S./Ireland tax treaty would likely apply assuming the Company avails itself of Treaty benefits under the U.S./Ireland tax treaty. Absent treaty benefits, the withholding rate on outbound dividends would be 30%. Currently, however, no withholding taxes are accrued with respect to such unremitted earnings as management has no intention of remitting these earnings. Similarly, no foreign income taxes have been provided on the un-remitted earnings of the Company's U.S. subsidiaries as management has neither the intention of remitting these earnings, nor would any Ireland tax be due, as any Irish tax would be expected to be fully offset by credit for taxes paid to the U.S. An estimate of the cumulative amount of U.S. earnings that would be subject to withholding tax, if distributed outside of the U.S., is approximately $846.8 million. The associated withholding tax liability under the U.S./Ireland tax treaty would be approximately $42.3 million.

Essent is not subject to income taxation other than as stated above. There can be no assurance that there will not be changes in applicable laws, regulations, or treaties which might require Essent to change the way it operates or becomes subject to taxation.

At December 31, 2017 and 2016, the Company had no unrecognized tax benefits. As of December 31, 2017, the U.S. federal income tax returns for the tax years 2014 through 2016 remain subject to examination. The Company has not recorded any uncertain tax positions as of December 31, 2017 or December 31, 2016.

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions The Company is a party to an investment advisory agreement with Goldman Sachs Asset Management, L.P., a subsidiary of The Goldman Sachs Group, Inc. ("Goldman Sachs"), one of Essent Group's investors prior to 2017. Through the date of our IPO, Goldman Sachs beneficially owned 11.35% of our outstanding shares. Subsequent to the IPO and prior to 2017, Goldman Sachs directly held less than 10% of our outstanding shares. Investment expense incurred under the investment advisory agreement totaled $0.8 million and $0.7 million for the years ended December 31, 2016 and 2015, respectively. Goldman Sachs is also one of several lenders under our Credit Facility discussed in Note 7 and was paid an upfront fee of $0.1 million in 2016. Commitment fees and interest expense incurred under the Credit Facility allocable to Goldman Sachs totaled $0.1 million in 2016.

Earnings per Share (EPS)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Earnings per Share (EPS)

The following table reconciles the net income and the weighted average common shares outstanding used in the computations of basic and diluted earnings per common share for the years ended December 31:



(In thousands, except per share amounts)	2017		2016		2015
Net income	$	379,747	$	222,606	$	157,331
Less: Common Shares dividends declared	—		—		—
Undistributed net income	$	379,747	$	222,606	$	157,331
Net income allocable to Common	$	379,747	$	222,606	$	157,331

Basic earnings per share	$	4.07	$	2.45	$	1.74
Diluted earnings per share	$	3.99	$	2.41	$	1.72
Basic weighted average Common Shares outstanding	93,330		90,913		90,351
Dilutive effect of nonvested shares	1,881		1,332		1,387
Diluted weighted average Common Shares outstanding	95,211		92,245		91,738

There were 44,540, 96,251 and 78,198 antidilutive shares for the years ended December 31, 2017, 2016 and 2015, respectively.

The nonvested performance-based share awards are considered contingently issuable for purposes of the EPS calculation. Based on the compounded annual book value per share growth as of December 31, 2017, 2016 and 2015, 100% of the performance-based share awards would be issuable under the terms of the arrangements at each date if December 31 was the end of the contingency period.

Accumulated Other Comprehensive Income (Loss)

12 Months Ended

Dec. 31, 2017

Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]

Accumulated Other Comprehensive Income (Loss)

The following table shows the rollforward of accumulated other comprehensive income (loss) for the year ended December 31:



	2017
(In thousands)	Before Tax			Tax Effect			Net of Tax
Balance at beginning of year	$	(14,436	)	$	2,181		$	(12,255	)
Other comprehensive income (loss):
Unrealized holding gains (losses) on investments:
Unrealized holding gains arising during the period	14,602			(5,239		)	9,363
Less: Reclassification adjustment for gains included in net income (1)	(2,015		)	720			(1,295		)
Net unrealized gains on investments	12,587			(4,519		)	8,068
Other comprehensive income	12,587			(4,519		)	8,068
Reclassification of certain income tax effects resulting from tax reform	—			935			935
Balance at end of year	$	(1,849	)	$	(1,403	)	$	(3,252	)



	2016
(In thousands)	Before Tax			Tax Effect			Net of Tax
Balance at beginning of year	$	661		$	(760	)	$	(99	)
Other comprehensive income (loss):
Unrealized holding gains (losses) on investments:
Unrealized holding losses arising during the period	(13,156		)	2,376			(10,780		)
Less: Reclassification adjustment for gains included in net income (1)	(1,941		)	565			(1,376		)
Net unrealized losses on investments	(15,097		)	2,941			(12,156		)
Other comprehensive loss	(15,097		)	2,941			(12,156		)
Balance at end of year	$	(14,436	)	$	2,181		$	(12,255	)

_______________________________________________________________________________


(1)	Included in net realized investments gains on our consolidated statements of comprehensive income.

Fair Value of Financial Instruments

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

We carry certain of our financial instruments at fair value. We define fair value as the current amount that would be exchanged to sell an asset or transfer a liability, other than in a forced liquidation.

Fair Value Hierarchy

ASC No. 820 specifies a hierarchy of valuation techniques based on whether the inputs to those valuation techniques are observable or unobservable. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect our market assumptions. The level within the fair value hierarchy to measure the financial instrument shall be determined based on the lowest level input that is significant to the fair value measurement. The three levels of the fair value hierarchy are as follows:


•	Level 1—Quoted prices for identical instruments in active markets accessible at the measurement date.


•	Level 2—Quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; and valuations in which all significant inputs are observable in active markets. Inputs are observable for substantially the full term of the financial instrument.


•	Level 3—Valuations derived from one or more significant inputs that are unobservable.

Determination of Fair Value

When available, we generally use quoted market prices to determine fair value and classify the financial instrument in Level 1. In cases where quoted market prices for similar financial instruments are available, we utilize these inputs for valuation techniques and classify the financial instrument in Level 2. In cases where quoted market prices are not available, fair values are based on estimates using discounted cash flows, present value or other valuation techniques. Those techniques are significantly affected by the assumptions used, including the discount rates and estimates of future cash flows and we classify the financial instrument in Level 3. Accordingly, the fair value estimates may not be realized in an immediate settlement of the instrument.

We used the following methods and assumptions in estimating fair values of financial instruments:

•

Investments available for sale—Investments available for sale are valued using quoted market prices in active markets, when available, and those investments are classified as Level 1 of the fair value hierarchy. Level 1 investments available for sale include investments such as U.S. Treasury securities and money market funds. Investments available for sale are classified as Level 2 of the fair value hierarchy if quoted market prices are not available and fair values are estimated using quoted prices of similar securities or recently executed transactions for the securities. U.S. agency securities, U.S. agency mortgage-backed securities, municipal debt securities, corporate debt securities, residential and commercial mortgage securities and asset-backed securities are classified as Level 2 investments.

We use independent pricing sources to determine the fair value of securities available for sale in Level 1 and Level 2 of the fair value hierarchy. We use one primary pricing service to provide individual security pricing based on observable market data and receive one quote per security. To ensure securities are appropriately classified in the fair value hierarchy, we review the pricing techniques and methodologies of the independent pricing service and believe that their policies adequately consider market activity, either based on specific transactions for the issue valued or based on modeling of securities with similar credit quality, duration, yield and structure that were recently traded. U.S. agency securities, U.S. agency mortgage-backed securities, municipal and corporate debt securities are valued by our primary vendor using recently executed transactions and proprietary models based on observable inputs, such as interest rate spreads, yield curves and credit risk. Residential and commercial mortgage securities and asset-backed securities are valued by our primary vendor using proprietary models based on observable inputs, such as interest rate spreads, prepayment speeds and credit risk. As part of our evaluation of investment prices provided by our primary pricing service, we obtained and reviewed their pricing methodologies which include a description of how each security type is evaluated and priced. We review the reasonableness of prices received from our primary pricing service by comparison to prices obtained from additional pricing sources. We have not made any adjustments to the prices obtained from our primary pricing service.

•

Derivative liabilities—Through June 30, 2016, certain of our Freddie Mac ACIS contracts were accounted for as derivatives. In determining an exit market, we considered the fact that there is not a principal market for these contracts. In the absence of a principal market, we valued these ACIS contracts in a hypothetical market where market participants, and potential counterparties, included other mortgage guaranty insurers or reinsurers with similar credit quality to us. We believed that in the absence of a principal market, this hypothetical market provided the most relevant information with respect to fair value estimates. These ACIS contracts were classified as Level 3 of the fair value hierarchy. During the quarter ended September 30, 2016, these contracts were amended and are now accounted for as insurance contracts rather than as derivatives. As of December 31, 2017 and 2016, the Company had no derivative instruments.

Through June 30, 2016, we determined the fair value of our derivative instruments primarily using internally-generated models. We utilized market observable inputs, such as the performance of the underlying pool of mortgages, mortgage prepayment speeds and pricing spreads on the reference STACR notes issued by Freddie Mac, whenever they were available. There was a high degree of uncertainty about our fair value estimates since our contracts were not traded or exchanged, which made external validation and corroboration of our estimates difficult. Considerable judgment was required to interpret market data to develop the estimates of fair value. Accordingly, the estimates may not have been indicative of amounts we could have realized in a market exchange or negotiated termination. The use of different market assumptions or estimation methodologies may have had a material effect on the estimated fair value amounts.

Assets and Liabilities Measured at Fair Value

All assets measured at fair value are categorized in the table below based upon the lowest level of significant input to the valuations. All fair value measurements at the reporting date were on a recurring basis.



December 31, 2017 (In thousands)	Quoted Prices in Active Markets for Identical Instruments (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Recurring fair value measurements
Financial Assets:
U.S. Treasury securities	$	227,805	$	—	$	—	$	227,805
U.S. agency securities	—		33,114		—		33,114
U.S. agency mortgage-backed securities	—		456,037		—		456,037
Municipal debt securities	—		465,255		—		465,255
Corporate debt securities	—		611,728		—		611,728
Residential and commercial mortgage securities	—		79,407		—		79,407
Asset-backed securities	—		167,922		—		167,922
Money market funds	263,797		—		—		263,797
Total assets at fair value	$	491,602	$	1,813,463	$	—	$	2,305,065



December 31, 2016 (In thousands)	Quoted Prices in Active Markets for Identical Instruments (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Recurring fair value measurements
Financial Assets:
U.S. Treasury securities	$	191,548	$	—	$	—	$	191,548
U.S. agency securities	—		18,441		—		18,441
U.S. agency mortgage-backed securities	—		316,494		—		316,494
Municipal debt securities	—		334,324		—		334,324
Corporate debt securities	—		456,357		—		456,357
Residential and commercial mortgage securities	—		68,336		—		68,336
Asset-backed securities	—		127,172		—		127,172
Money market funds	102,430		—		—		102,430
Total assets at fair value	$	293,978	$	1,321,124	$	—	$	1,615,102

Changes in Level 3 Recurring Fair Value Measurements

The following table presents changes during the years ended December 31, 2017 and 2016 in Level 3 liabilities measured at fair value on a recurring basis, and the net realized and unrealized losses (gains) related to the Level 3 liabilities in the consolidated balance sheets at December 31, 2017 and 2016. During the years ended December 31, 2017 and 2016, we had no Level 3 assets.



	Year Ended December 31,
(In thousands)	2017		2016
Level 3 Liabilities
Fair value of derivative liabilities at beginning of period	$	—	$	1,232
Net realized and unrealized losses (gains) included in income	—		(1,934		)
Other comprehensive (income) loss	—		—
Purchases, sales, issues and settlements, net	—		702
Gross transfers in	—		—
Gross transfers out	—		—
Fair value of derivative liabilities at end of period	$	—	$	—

Changes in net unrealized losses (gains) included in income on instruments held at end of period	$	—	$	(1,934	)

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Statutory Accounting

12 Months Ended

Dec. 31, 2017

Insurance [Abstract]

Statutory Accounting

Our U.S. insurance subsidiaries prepare statutory-basis financial statements in accordance with the accounting practices prescribed or permitted by their respective state’s department of insurance, which is a comprehensive basis of accounting other than GAAP. We did not use any prescribed or permitted statutory accounting practices (individually or in the aggregate) that resulted in reported statutory surplus or capital that was significantly different from the statutory surplus or capital that would have been reported had National Association of Insurance Commissioners’ statutory accounting practices been followed. The following table presents Essent Guaranty’s and Essent PA’s statutory net income, statutory surplus and contingency reserve liability as of and for the years ended December 31:



(In thousands)	2017		2016		2015
Essent Guaranty
Statutory net income	$	261,811	$	215,951	$	172,688
Statutory surplus	761,006		578,887		522,172
Contingency reserve liability	678,701		480,829		315,058

Essent PA
Statutory net income	$	10,250	$	12,978	$	15,200
Statutory surplus	45,509		47,387		47,139
Contingency reserve liability	43,141		36,401		27,502

Net income determined in accordance with statutory accounting practices differs from GAAP. In 2017 and 2016, the more significant differences between net income determined under statutory accounting practices and GAAP for Essent Guaranty and Essent PA relate to policy acquisition costs and income taxes. Under statutory accounting practices, policy acquisition costs are expensed as incurred while such costs are capitalized and amortized to expense over the life of the policy under GAAP. As discussed in Note 12, we are eligible for a tax deduction, subject to certain limitations for amounts required by state law or regulation to be set aside in statutory contingency reserves when we purchase T&L Bonds. Under statutory accounting practices, this deduction reduces the tax provision recorded by Essent Guaranty and Essent PA and, as a result, increases statutory net income and surplus as compared to net income and equity determined in accordance with GAAP.

At December 31, 2017 and 2016, the statutory capital of our U.S. insurance subsidiaries, which is defined as the total of statutory surplus and contingency reserves, was in excess of the statutory capital necessary to satisfy their regulatory requirements.

Effective December 31, 2015, Fannie Mae and Freddie Mac, at the direction of the Federal Housing Finance Agency, implemented new coordinated Private Mortgage Insurer Eligibility Requirements, which we refer to as the "PMIERs." The PMIERs represent the standards by which private mortgage insurers are eligible to provide mortgage insurance on loans owned or guaranteed by Fannie Mae and Freddie Mac. The PMIERs include financial strength requirements incorporating a risk-based framework that require approved insurers to have a sufficient level of liquid assets from which to pay claims. The PMIERs also include enhanced operational performance expectations and define remedial actions that apply should an approved insurer fail to comply with these requirements. As of December 31, 2017, Essent Guaranty, our GSE-approved mortgage insurance company, was in compliance with the PMIERs.

Statement of Statutory Accounting Principles No. 58, Mortgage Guaranty Insurance, requires mortgage insurers to establish a special contingency reserve for statutory accounting purposes included in total liabilities equal to 50% of earned premium for that year. During 2017, Essent Guaranty increased its contingency reserve by $197.9 million and Essent PA increased its contingency reserve by $6.7 million. This reserve is required to be maintained for a period of 120 months to protect against the effects of adverse economic cycles. After 120 months, the reserve is released to unassigned funds. In the event an insurer’s loss ratio in any calendar year exceeds 35%, however, the insurer may, after regulatory approval, release from its contingency reserves an amount equal to the excess portion of such losses. Essent Guaranty and Essent PA did not release any amounts from their contingency reserves in 2017, 2016 or 2015.

Under The Insurance Act 1978, as amended, and related regulations of Bermuda (the "Insurance Act"), Essent Re is required to annually prepare statutory financial statements and a statutory financial return in accordance with the financial reporting provisions of the Insurance Act, which is a basis other than GAAP. The Insurance Act also requires that Essent Re maintain minimum share capital of $1 million and must ensure that the value of its general business assets exceeds the amount of its general business liabilities by an amount greater than the prescribed minimum solvency margins and enhanced capital requirement pertaining to its general business. At December 31, 2017 and 2016, all such requirements were met.

Essent Re's statutory capital and surplus was $662.6 million and $401.1 million as of December 31, 2017 and 2016, respectively, and statutory net income was $96.9 million and $56.7 million, respectively. Statutory capital and surplus and net income determined in accordance with statutory accounting practices were not significantly different than the amounts determined under GAAP.

Capital Maintenance Agreement	12 Months Ended
Capital Maintenance Agreement	Dec. 31, 2017
Insurance Ratios [Abstract]
Capital Maintenance Agreement	Capital Maintenance Agreement Essent Guaranty has a capital maintenance agreement with Essent PA under which Essent Guaranty agreed to contribute funds, under specified conditions, to maintain Essent PA's risk-to-capital ratio at or below 25.0 to 1 in return for a surplus note. As of December 31, 2017, Essent PA's risk-to-capital ratio was 5.4:1 and there were no amounts outstanding related to this agreement.

Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Data (Unaudited)

The following table summarizes the unaudited results of operations for each quarter of 2017 and 2016. We have prepared the consolidated quarterly information on a basis consistent with the audited consolidated financial statements. In the opinion of management, the financial information reflects all adjustments (which include normal recurring adjustments) required for a fair presentation of the financial information for the quarters presented. This information should be read in conjunction with our audited financial statements and the related notes. The results of interim periods are not necessarily indicative of the results for the full year.



	2017
(In thousands, except per share amounts)	December 31		September 30		June 30		March 31
Net premiums earned	$	147,976	$	137,940	$	126,563	$	117,651
Other revenues	13,134		12,263		11,043		9,941
Provision for losses and LAE	17,456		4,313		1,770		3,693
Other underwriting and operating expenses	36,480		37,035		35,686		36,332
Interest expense	1,817		1,456		1,189		716
Income before income taxes	105,357		107,399		98,961		86,851
Net income	162,638		78,393		72,118		66,598
Basic earnings per Common Share	$	1.69	$	0.83	$	0.79	$	0.73
Diluted earnings per Common Share	$	1.65	$	0.82	$	0.77	$	0.72
Basic weighted average Common Shares outstanding	96,429		94,185		91,381		91,258
Diluted weighted average Common Shares outstanding	98,497		96,094		93,162		93,023



	2016
(In thousands, except per share amounts)	December 31		September 30		June 30		March 31
Net premiums earned	$	116,792	$	110,801	$	100,711	$	94,403
Other revenues	9,581		10,453		7,454		8,063
Provision for losses and LAE	3,865		4,965		2,964		3,731
Other underwriting and operating expenses	34,836		32,792		31,409		31,388
Interest expense	370		56		—		—
Income before income taxes	87,302		83,441		73,792		67,347
Net income	62,686		59,711		52,258		47,951
Basic earnings per Common Share	$	0.69	$	0.66	$	0.57	$	0.53
Diluted earnings per Common Share	$	0.68	$	0.65	$	0.57	$	0.52
Basic weighted average Common Shares outstanding	90,991		90,961		90,912		90,785
Diluted weighted average Common Shares outstanding	92,577		92,399		92,138		91,859

Schedule I-Summary of Investments-Other Than Investments in Related Parties

12 Months Ended

Dec. 31, 2017

Summary of Investments, Other than Investments in Related Parties [Abstract]

Schedule I-Summary of Investments-Other Than Investments in Related Parties

Schedule I—Summary of Investments—Other Than Investments in Related Parties

December 31, 2017



Type of Investment (In thousands)	Amortized Cost		Fair Value		Amount at which shown in the Balance Sheet
Fixed maturities:
Bonds:
United States Government and government agencies and authorities	$	679,654	$	668,059	$	668,059
States, municipalities and political subdivisions	457,418		465,255		465,255
Residential and commercial mortgage securities	78,974		79,407		79,407
Asset-backed securities	167,638		167,922		167,922
All other corporate bonds	610,516		611,728		611,728
Total fixed maturities	1,994,200		1,992,371		1,992,371
Short-term investments	312,714		312,694		312,694
Total investments	$	2,306,914	$	2,305,065	$	2,305,065

Schedule II-Condensed Financial Information of Registrant

12 Months Ended

Dec. 31, 2017

Condensed Financial Information of Parent Company Only Disclosure [Abstract]

Schedule II-Condensed Financial Information of Registrant

Schedule II—Condensed Financial Information of Registrant

Balance Sheets

Parent Company Only



	December 31,
(In thousands)	2017			2016
Assets
Investments
Fixed maturities (amortized cost: 2017 — $0; 2016 — $10,002)	$	—		$	10,004
Short-term investments (amortized cost: 2017 — $97,926; 2016 — $32,039)	97,917			32,036
Total investments	97,917			42,040
Cash	6,250			4,521
Due from affiliates	987			1,750
Investment in consolidated subsidiaries	1,956,955			1,393,720
Other assets	2,662			2,452
Total Assets	$	2,064,771		$	1,444,483

Liabilities and stockholders' equity
Liabilities
Credit facility borrowings (at carrying value, less unamortized deferred costs of $1,409 in 2017 and $0 in 2016)	$	123,591		$	100,000
Other accrued liabilities	744			710
Total liabilities	124,335			100,710
Commitments and contingencies
Stockholders' Equity
Common shares	1,476			1,397
Additional paid-in capital	1,127,137			918,296
Accumulated other comprehensive loss	(3,252		)	(12,255		)
Retained earnings	815,075			436,335
Total stockholders' equity	1,940,436			1,343,773
Total liabilities and stockholders' equity	$	2,064,771		$	1,444,483

See accompanying supplementary notes to Parent Company condensed

financial information and the consolidated financial statements and notes thereto.

Schedule II—Condensed Financial Information of Registrant

Condensed Statements of Comprehensive Income

Parent Company Only



	Year Ended December 31,
(In thousands)	2017			2016			2015
Revenues:
Net investment income	$	494		$	284		$	421
Realized investment (losses) gains, net	(2		)	111			(181		)
Administrative service fees from subsidiaries	489			473			437
Total revenues	981			868			677
Expenses:
Administrative service fees to subsidiaries	2,127			1,760			1,762
Other operating expenses	4,968			4,832			3,554
Interest expense	4,371			426			—
Total expenses	11,466			7,018			5,316
Loss before income taxes and equity in undistributed net income in subsidiaries	(10,485		)	(6,150		)	(4,639		)
Loss before equity in undistributed net income of subsidiaries	(10,485		)	(6,150		)	(4,639		)
Equity in undistributed net income of subsidiaries	390,232			228,756			161,970
Net income	$	379,747		$	222,606		$	157,331
Other comprehensive income (loss):
Change in unrealized appreciation (depreciation) of investments, net of tax expense (benefit) of $4,519 in 2017, ($2,941) in 2016 and ($1,285) in 2015	8,068			(12,156		)	(4,766		)
Total other comprehensive income (loss)	8,068			(12,156		)	(4,766		)
Comprehensive income	$	387,815		$	210,450		$	152,565

See accompanying supplementary notes to Parent Company condensed

financial information and the consolidated financial statements and notes thereto.

Schedule II—Condensed Financial Information of Registrant

Condensed Statements of Cash Flows

Parent Company Only



	Year Ended December 31,
(In thousands)	2017			2016			2015
Operating Activities
Net income	$	379,747		$	222,606		$	157,331
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in net income of subsidiaries	(390,232		)	(228,756		)	(161,970		)
Loss (gain) on the sale of investments, net	2			(111		)	181
Stock-based compensation expense	807			880			880
Amortization of premium on investment securities	—			169			399
Changes in assets and liabilities:
Other assets	1,421			121			(40		)
Other accrued liabilities	18,236			17,433			15,153
Net cash provided by operating activities	9,981			12,342			11,934
Investing Activities
Net change in short-term investments	(65,887		)	(6,525		)	91,119
Investments in subsidiaries	(164,927		)	(130,101		)	(61,328		)
Purchase of investments available for sale	—			—			(130,461		)
Proceeds from maturity of investments available for sale	10,000			10,000			—
Proceeds from sales of investments available for sale	—			16,582			94,429
Net cash used in investing activities	(220,814		)	(110,044		)	(6,241		)
Financing Activities
Issuance of common shares, net of costs	197,829			—			(537		)
Credit facility borrowings	75,000			100,000			—
Credit facility repayments	(50,000		)	—			—
Treasury stock acquired	(7,577		)	(4,024		)	(5,168		)
Payment of issuance costs for credit facility	(2,690		)	(2,436		)	—
Other financing activities	—			142			53
Net cash provided by (used in) financing activities	212,562			93,682			(5,652		)
Net increase (decrease) in cash	1,729			(4,020		)	41
Cash at beginning of year	4,521			8,541			8,500
Cash at end of year	$	6,250		$	4,521		$	8,541

Supplemental Disclosure of Cash Flow Information
Interest payments	$	(4,045	)	$	(324	)	$	—

Noncash Transactions
Repayment of borrowings with term loan proceeds (see Note C)	$	(125,000	)	$	—		$	—

See accompanying supplementary notes to Parent Company condensed

financial information and the consolidated financial statements and notes thereto.

Schedule II—Condensed Financial Information of Registrant

Parent Company Only

Supplementary Notes

Note A

The accompanying Parent Company financial statements should be read in conjunction with the consolidated financial statements and notes to consolidated financial statements. These financial statements have been prepared on the same basis and using the same accounting policies as described in the consolidated financial statements included herein, except that the Parent Company uses the equity-method of accounting for its majority-owned subsidiaries.

Note B

Under the insurance laws of the Commonwealth of Pennsylvania, the insurance subsidiaries may pay dividends during any 12-month period in an amount equal to the greater of (i) 10% of the preceding year-end statutory policyholders' surplus or (ii) the preceding year's statutory net income. The Pennsylvania statute also requires that dividends and other distributions be paid out of positive unassigned surplus without prior approval. As of December 31, 2017, Essent Guaranty had unassigned surplus of approximately $70.7 million. Essent PA had unassigned surplus of approximately $6.5 million as of December 31, 2017.

During the three years ending December 31, 2017, the Parent Company did not receive any dividends from its subsidiaries.

Note C

As more fully discussed in Note 7 of our consolidated financial statements, during 2017, the Parent Company and its subsidiaries entered into an amended and restated four-year, secured credit facility with a committed capacity of $375 million (the “Credit Facility”). The Credit Facility amends and restates the three-year, secured revolving credit facility entered into on April 19, 2016, and provides for (i) an increase in the revolving credit facility from $200 million to $250 million, (ii) the issuance of term loans of $125 million, the proceeds of which were used at closing to pay down borrowings outstanding under the revolving credit facility, and (iii) a $75 million uncommitted line that may be exercised at the Borrowers’ option so long as the Borrowers receive commitments from the lenders. At December 31, 2017, the Parent Company's borrowings under the Credit Facility contractually mature in 2021.

- Definition

The entire disclosure for condensed financial information, including the financial position, cash flows, and the results of operations of the registrant (parent company) as of the same dates or for the same periods for which audited consolidated financial statements are being presented. Alternatively, the details of this disclosure can be reported by the specific parent company taxonomy elements, indicating the appropriate date and period contexts in an instance document.

+ References + Details

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2017
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates.
Investments Available for Sale	Investments Available for Sale Investments available for sale include securities that we sell from time to time to provide liquidity and in response to changes in the market. Debt and equity securities classified as available for sale are reported at fair value with unrealized gains and losses on these securities reported in other comprehensive income, net of deferred income taxes. See Note 16 for a description of the valuation methods for investments available for sale. We monitor our fixed maturities for unrealized losses that appear to be other-than-temporary. A fixed maturity security is considered to be other-than-temporarily impaired when the security's fair value is less than its amortized cost basis and 1) we intend to sell the security, 2) it is more likely than not that we will be required to sell the security before recovery of the security's amortized cost basis, or 3) we believe we will be unable to recover the entire amortized cost basis of the security (i.e., a credit loss has occurred). When we determine that a credit loss has been incurred, but we do not intend to sell the security and it is not more likely than not that we will be required to sell the security before recovery of the security's amortized cost basis, the portion of the other-than-temporary impairment that is credit related is recorded as a realized loss in the consolidated statements of comprehensive income, and the portion of the other-than-temporary impairment that is not credit related is included in other comprehensive income. For those fixed maturities for which an other-than-temporary impairment has occurred, we adjust the amortized cost basis of the security and record a realized loss in the consolidated statements of comprehensive income. We recognize purchase premiums and discounts in interest income using the interest method over the term of the securities. Gains and losses on the sales of securities are recorded on the trade date and are determined using the specific identification method. Short-term investments are defined as short-term, highly liquid investments, both readily convertible to cash and having maturities at acquisition of twelve months or less.
Long-Lived Assets	Long-Lived Assets Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is calculated using the straight-line method over the estimated useful lives of the assets. Repairs and maintenance are charged to expense as incurred. Estimated useful lives are 5 years for furniture and fixtures and 2 to 3 years for equipment, computer hardware and purchased software. Certain costs associated with the acquisition or development of internal-use software are capitalized. Once the software is ready for its intended use, these costs are amortized on a straight-line basis over the software's expected useful life, which is generally 3 years. We amortize leasehold improvements over the shorter of the lives of the leases or estimated service lives of the leasehold improvements.
Deferred Policy Acquisition Costs	Deferred Policy Acquisition Costs We defer certain personnel costs and premium tax expense directly related to the successful acquisition of new insurance policies and amortize these costs over the period the related estimated gross profits are recognized in order to match costs and revenues. We do not defer any underwriting costs associated with our contract underwriting services. Costs related to the acquisition of mortgage insurance business are initially deferred and reported as deferred policy acquisition costs. Consistent with industry accounting practice, amortization of these costs for each underwriting year book of business is recognized in proportion to estimated gross profits. Estimated gross profits are composed of earned premium, interest income, losses and loss adjustment expenses. The deferred costs are adjusted as appropriate for policy cancellations to be consistent with our revenue recognition policy. We estimate the rate of amortization to reflect actual experience and any changes to persistency or loss development. Deferred policy acquisition costs are reviewed periodically to determine that they do not exceed recoverable amounts, after considering investment income.
Insurance Premium Revenue Recognition	Insurance Premium Revenue Recognition Mortgage guaranty insurance policies are contracts that are generally non-cancelable by the insurer, are renewable at a fixed price, and provide for payment of premium on a monthly, annual or single basis. Upon renewal, we are not able to re-underwrite or re-price our policies. Consistent with industry accounting practices, premiums written on a monthly basis are earned as coverage is provided. Monthly policies accounted for 86% of earned premium in 2017. Premiums written on an annual basis are amortized on a pro rata basis over the year of coverage. Primary mortgage insurance written on policies covering more than one year are referred to as single premium policies. A portion of the revenue from single premium policies is recognized in earned premium in the current period, and the remaining portion is deferred as unearned premium and earned over the expected life of the policy. If single premium policies related to insured loans are cancelled due to repayment by the borrower, and the premium is non-refundable, then the remaining unearned premium related to each cancelled policy is recognized as earned premium upon notification of the cancellation.
Reserve for Losses and Loss Adjustment Expenses	Reserve for Losses and Loss Adjustment Expenses We establish reserves for losses based on our best estimate of ultimate claim costs for defaulted loans using the general principles contained in ASC No. 944, in accordance with industry practice. However, consistent with industry standards for mortgage insurers, we do not establish loss reserves for future claims on insured loans which are not currently in default. Loans are classified as in default when the borrower has missed two consecutive payments. Once we are notified that a borrower has defaulted, we will consider internal and third-party information and models, including the status of the loan as reported by its servicer and the type of loan product to determine the likelihood that a default will reach claim status. In addition, we will project the amount that we will pay if a default becomes a claim (referred to as "claim severity"). Based on this information, at each reporting date we determine our best estimate of loss reserves at a given point in time. Included in loss reserves are reserves for incurred but not reported ("IBNR") claims. IBNR reserves represent our estimated unpaid losses on loans that are in default, but have not yet been reported to us as delinquent by our customers. We will also establish reserves for associated loss adjustment expenses, consisting of the estimated cost of the claims administration process, including legal and other fees and expenses associated with administering the claims process. Establishing reserves is inherently subjective as it requires estimates that are susceptible to significant revision as more information becomes available. Our estimates of claim rates and claim sizes will be strongly influenced by prevailing economic conditions, such as the overall state of the economy, current rates or trends in unemployment, changes in housing values and/or interest rates, and our best judgments as to the future values or trends of these macroeconomic factors. Losses incurred are also generally affected by the characteristics of our insured loans, such as the loan amount, loan-to-value ratio, the percentage of coverage on the insured loan and the credit quality of the borrower.
Premium Deficiency Reserve	Premium Deficiency Reserve We are required to establish a premium deficiency reserve if the net present value of the expected future losses and expenses for a particular group of policies exceeds the net present value of expected future premium, anticipated investment income and existing reserves for that specified group of policies. We reassess our expectations for premium, losses and expenses of our mortgage insurance business periodically and update our premium deficiency analysis accordingly.
Derivative Instruments	Derivative Instruments Through June 30, 2016, insurance and certain reinsurance policies issued by Essent Re in connection with Freddie Mac's Agency Credit Insurance Structure ("ACIS") program were accounted for as derivatives under GAAP with the fair value of these policies reported as an asset or liability and changes in the fair value of these policies reported in earnings as a component of other income. During the quarter ended September 30, 2016, these contracts were amended and are accounted for as insurance contracts rather than as derivatives subsequent to their amendment.
Stock-Based Compensation	Stock-Based Compensation We measure the cost of employee services received in exchange for awards of equity instruments at the grant date of the award using a fair value based method. Prior to our initial public offering, we estimated the fair value of each nonvested share grant on the date of grant based on management's best estimate using methods further described in Note 10 of our consolidated financial statements. Subsequent to our initial public offering, fair value is determined on the date of grant based on quoted market prices. We recognize compensation expense on nonvested shares over the vesting period of the award. We adopted ASU 2016-09 Improvements to Employee Share-Based Payment Accounting (Topic 718) on January 1, 2017 and recorded a charge of $0.1 million to retained earnings as of that date representing a cumulative-effect adjustment associated with our election to recognize forfeitures as they occur rather than on an estimated basis. In connection with the adoption of this ASU, beginning in 2017, excess tax benefits and tax deficiencies associated with share-based payments are recognized as income tax expense or benefit in the income statement and treated as discrete items in the reporting period. Through December 31, 2016, excess tax benefits were recognized in additional paid-in-capital.
Income Taxes	Income Taxes Deferred income tax assets and liabilities are determined using the asset and liability (or balance sheet) method. Under this method, we determine the net deferred tax asset or liability based on the tax effects of the temporary differences between the book and tax bases of the various assets and liabilities and give current recognition to changes in tax rates and laws. Changes in tax laws, rates, regulations and policies, or the final determination of tax audits or examinations, could materially affect our tax estimates. We evaluate the realizability of the deferred tax asset and recognize a valuation allowance if, based on the weight of all available positive and negative evidence, it is more likely than not that some portion or all of the deferred tax asset will not be realized. When evaluating the realizability of the deferred tax asset, we consider estimates of expected future taxable income, existing and projected book/tax differences, carryback and carryforward periods, tax planning strategies available, and the general and industry specific economic outlook. This realizability analysis is inherently subjective, as it requires management to forecast changes in the mortgage market, as well as the related impact on mortgage insurance, and the competitive and general economic environment in future periods. Changes in the estimate of deferred tax asset realizability, if applicable, are included in income tax expense on the consolidated statements of comprehensive income. ASC No. 740 provides a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. In accordance with ASC No. 740, before a tax benefit can be recognized, a tax position is evaluated using a threshold that it is more likely than not that the tax position will be sustained upon examination. When evaluating the more-likely-than-not recognition threshold, ASC No. 740 provides that a company should presume the tax position will be examined by the appropriate taxing authority that has full knowledge of all relevant information. If the tax position meets the more-likely-than-not recognition threshold, it is initially and subsequently measured as the largest amount of benefit that is greater than 50% likely of being realized upon ultimate settlement. As described in Note 12, we purchase non-interest-bearing United States Mortgage Guaranty Tax and Loss Bonds ("T&L Bonds") issued by the Treasury Department. These assets are carried at cost and are reported as prepaid federal income tax on the consolidated balance sheets. It is our policy to classify interest and penalties as income tax expense.
Earnings per Share	Earnings per Share Basic earnings per common share amounts are calculated based on income available to common stockholders and the weighted average number of common shares outstanding during the reporting period. Diluted earnings per common share amounts are calculated based on income available to common stockholders and the weighted average number of common and potential common shares outstanding during the reporting period. Potential common shares, composed of the incremental common shares issuable upon vesting of unvested common shares and common share units, are included in the earnings per share calculation to the extent that they are dilutive.
Recently Issued Accounting Standards	Recently Issued Accounting Standards In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") ASU 2014-09, Revenue from Contracts with Customers (Topic 606). This update is intended to provide a consistent approach in recognizing revenue. In accordance with the new standard, recognition of revenue occurs when a customer obtains control of promised goods or services in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In addition, the new standard requires that reporting companies disclose the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. In July 2015, the FASB delayed the effective date for this update to interim and annual periods beginning after December 15, 2017. In December 2016, the FASB clarified that all contracts that are within the scope of Topic 944, Financial Services-Insurance, are excluded from the scope of ASU 2014-09. Accordingly, this update will not impact the recognition of revenue related to insurance premiums or investments, which represent a significant portion of our total revenues. The adoption of this ASU is not expected to have a material effect on the Company's consolidated operating results or financial position. In January 2016, the FASB issued ASU 2016-01, Financial Instruments-Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. This update requires certain equity investments (except those accounted for under the equity method of accounting or result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income. An entity may choose to measure equity investments that do not have readily determinable fair values at cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. A qualitative assessment for impairment is required for equity investments without readily determinable fair values. This update also requires public entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes. In addition, an entity is required to evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale investment securities in combination with the entity’s other deferred tax assets. The provisions of this update are effective for interim and annual periods beginning after December 15, 2017. The adoption of this ASU is not expected to have a material effect on the Company's consolidated operating results or financial position. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). This update will require organizations that lease assets to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases. The new guidance will also require additional disclosures about the amount, timing and uncertainty of cash flows arising from leases. The provisions of this update are effective for annual and interim periods beginning after December 15, 2018. The Company expects a gross-up of its consolidated balance sheets as a result of recognizing lease liabilities and right of use assets. The Company is still evaluating the impact the adoption of this ASU will have on the consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Measurement of Credit Losses on Financial Instruments (Topic 326). This update is intended to provide financial statement users with more information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. The amendments in this ASU replace the incurred loss impairment methodology in current GAAP with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. The new guidance requires financial assets measured at amortized cost to be presented at the net amount expected to be collected through the use of an allowance for credit losses. Credit losses relating to available-for-sale debt securities will also be recorded through an allowance rather than as a write-down of the amortized cost of the securities. The provisions of this update are effective for annual and interim periods beginning after December 15, 2019. While the Company is still evaluating this ASU, we do not expect it to impact our accounting for insurance losses and loss adjustment expenses ("LAE") as these items are not within the scope of this ASU. In February 2018, the FASB issued ASU 2018-02, Income Statement- Reporting Comprehensive Income (Topic 220). This update permits entities to elect to reclassify the income tax effects of the Tax Cuts and Jobs Act (“TCJA”) on items within accumulated other comprehensive income to retained earnings. The provisions of this update are effective for annual and interim periods beginning after December 15, 2018 and early adoption is permitted. The Company adopted this ASU retrospective to 2017 and elected to reclassify the income tax effects of TCJA, totaling $0.9 million, from accumulated other comprehensive income to retained earnings. It is the Company’s policy to use the portfolio approach to release income tax effects from accumulated other comprehensive income.

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Schedule of balances by type of long-lived assets

The balances by type were as follows at December 31:



	2017					2016
(In thousands)	Cost		Accumulated Depreciation/ Amortization			Cost		Accumulated Depreciation/ Amortization
Furniture and fixtures	$	2,074	$	(1,592	)	$	2,042	$	(1,298	)
Office equipment	640		(602		)	625		(513		)
Computer hardware	6,837		(5,413		)	5,700		(4,260		)
Purchased software	35,710		(34,620		)	35,148		(33,304		)
Costs of internal-use software	7,965		(6,773		)	7,140		(6,075		)
Leasehold improvements	4,219		(1,466		)	4,007		(1,093		)
Total	$	57,445	$	(50,466	)	$	54,662	$	(46,543	)

Investments Available for Sale (Tables)

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Schedule of investments available for sale

Investments available for sale consist of the following:



December 31, 2017 (In thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
U.S. Treasury securities	$	231,905	$	2	$	(4,102	)	$	227,805
U.S. agency securities	33,669		—		(555		)	33,114
U.S. agency mortgage-backed securities	462,986		567		(7,516		)	456,037
Municipal debt securities(1)	457,418		9,098		(1,261		)	465,255
Corporate debt securities(2)	610,516		4,249		(3,037		)	611,728
Residential and commercial mortgage securities	78,974		791		(358		)	79,407
Asset-backed securities	167,638		467		(183		)	167,922
Money market funds	263,808		—		(11		)	263,797
Total investments available for sale	$	2,306,914	$	15,174	$	(17,023	)	$	2,305,065



December 31, 2016 (In thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
U.S. Treasury securities	$	195,990	$	55	$	(4,497	)	$	191,548
U.S. agency securities	18,785		—		(344		)	18,441
U.S. agency mortgage-backed securities	324,654		335		(8,495		)	316,494
Municipal debt securities(1)	334,048		3,649		(3,373		)	334,324
Corporate debt securities(2)	457,842		2,343		(3,828		)	456,357
Residential and commercial mortgage securities	68,430		488		(582		)	68,336
Asset-backed securities	127,359		260		(447		)	127,172
Money market funds	102,430		—		—			102,430
Total investments available for sale	$	1,629,538	$	7,130	$	(21,566	)	$	1,615,102

_______________________________________________________________________________



	December 31,		December 31,
(1) The following table summarizes municipal debt securities as of :	2017		2016
Special revenue bonds	63.6	%	63.6	%
General obligation bonds	30.7		29.7
Certificate of participation bonds	4.4		4.9
Tax allocation bonds	0.8		1.1
Special tax bonds	0.5		0.7
Total	100.0	%	100.0	%



	December 31,		December 31,
(2) The following table summarizes corporate debt securities as of :	2017		2016
Financial	45.9	%	40.6	%
Consumer, non-cyclical	16.2		18.6
Energy	7.8		9.3
Communications	7.3		6.0
Industrial	6.3		5.6
Consumer, cyclical	5.3		6.3
Utilities	5.3		6.0
Technology	3.9		4.3
Basic materials	2.0		3.3
Total	100.0	%	100.0	%

Schedule of amortized cost and fair value of investments available for sale by contractual maturity



(In thousands)	Amortized Cost		Fair Value
U.S. Treasury securities:
Due in 1 year	$	58,429	$	58,411
Due after 1 but within 5 years	72,469		71,661
Due after 5 but within 10 years	71,006		68,376
Due after 10 years	30,001		29,357
Subtotal	231,905		227,805
U.S. agency securities:
Due in 1 year	—		—
Due after 1 but within 5 years	33,669		33,114
Subtotal	33,669		33,114
Municipal debt securities:
Due in 1 year	33,038		32,998
Due after 1 but within 5 years	97,637		97,831
Due after 5 but within 10 years	179,245		183,610
Due after 10 years	147,498		150,816
Subtotal	457,418		465,255
Corporate debt securities:
Due in 1 year	80,177		80,093
Due after 1 but within 5 years	332,105		331,790
Due after 5 but within 10 years	196,289		197,848
Due after 10 years	1,945		1,997
Subtotal	610,516		611,728
U.S. agency mortgage-backed securities	462,986		456,037
Residential and commercial mortgage securities	78,974		79,407
Asset-backed securities	167,638		167,922
Money market funds	263,808		263,797
Total investments available for sale	$	2,306,914	$	2,305,065

Schedule of realized gross gains and losses on sale of investments available for sale

Gross gains and losses realized on the sale of investments available for sale were as follows:



	Year Ended December 31,
(In thousands)	2017		2016		2015
Realized gross gains	$	2,504	$	2,822	$	3,908
Realized gross losses	425		788		1,073

Schedule of fair value of investments in an unrealized loss position and related unrealized losses

The fair value of investments in an unrealized loss position and the related unrealized losses were as follows:



	Less than 12 months					12 months or more					Total
December 31, 2017 (In thousands)	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
U.S. Treasury securities	$	151,119	$	(1,240	)	$	69,454	$	(2,862	)	$	220,573	$	(4,102	)
U.S. agency securities	17,320		(190		)	15,794		(365		)	33,114		(555		)
U.S. agency mortgage-backed securities	180,443		(1,394		)	217,944		(6,122		)	398,387		(7,516		)
Municipal debt securities	124,171		(817		)	23,492		(444		)	147,663		(1,261		)
Corporate debt securities	214,371		(1,213		)	94,261		(1,824		)	308,632		(3,037		)
Residential and commercial mortgage securities	29,842		(179		)	5,988		(179		)	35,830		(358		)
Asset-backed securities	58,798		(133		)	5,828		(50		)	64,626		(183		)
Money market funds	59,489		(11		)	—		—			59,489		(11		)
Total	$	835,553	$	(5,177	)	$	432,761	$	(11,846	)	$	1,268,314	$	(17,023	)



	Less than 12 months					12 months or more					Total
December 31, 2016 (In thousands)	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
U.S. Treasury securities	$	160,018	$	(4,497	)	$	—	$	—		$	160,018	$	(4,497	)
U.S. agency securities	18,441		(344		)	—		—			18,441		(344		)
U.S. agency mortgage-backed securities	289,282		(8,402		)	1,812		(93		)	291,094		(8,495		)
Municipal debt securities	149,368		(3,351		)	6,015		(22		)	155,383		(3,373		)
Corporate debt securities	213,965		(3,704		)	8,344		(124		)	222,309		(3,828		)
Residential and commercial mortgage securities	18,026		(434		)	14,014		(148		)	32,040		(582		)
Asset-backed securities	28,294		(57		)	47,597		(390		)	75,891		(447		)
Total	$	877,394	$	(20,789	)	$	77,782	$	(777	)	$	955,176	$	(21,566	)

Schedule of net investment income

Net investment income consists of:



	Year Ended December 31,
(In thousands)	2017			2016			2015
Fixed maturities	$	41,935		$	29,865		$	21,693
Short-term investments	1,019			142			63
Gross investment income	42,954			30,007			21,756
Investment expenses	(2,728		)	(2,117		)	(1,871		)
Net investment income	$	40,226		$	27,890		$	19,885

Accounts Receivable (Tables)

12 Months Ended

Dec. 31, 2017

Receivables [Abstract]

Schedule of accounts receivable

Accounts receivable consists of the following at December 31:



(In thousands)	2017		2016
Premiums receivable	$	29,027	$	21,265
Other receivables	725		367
Total accounts receivable	29,752		21,632
Less: Allowance for doubtful accounts	—		—
Accounts receivable, net	$	29,752	$	21,632

Reserve for Losses and Loss Adjustment Expenses (Tables)

12 Months Ended

Dec. 31, 2017

Liability for Future Policy Benefits and Unpaid Claims and Claims Adjustment Expense [Abstract]

Schedule of reconciliation of beginning and ending reserve balances for losses and loss adjustment expenses (LAE)

The following table provides a reconciliation of the beginning and ending reserve balances for losses and loss adjustment expenses ("LAE") for the years ended December 31:



($ in thousands)	2017			2016
Reserve for losses and LAE at beginning of year	$	28,142		$	17,760
Less: Reinsurance recoverables	—			—
Net reserve for losses and LAE at beginning of year	28,142			17,760
Add provision for losses and LAE, net of reinsurance, occurring in:
Current year	38,178			21,889
Prior years	(10,946		)	(6,364		)
Net incurred losses during the current year	27,232			15,525
Deduct payments for losses and LAE, net of reinsurance, occurring in:
Current year	633			927
Prior years	7,891			4,216
Net loss and LAE payments during the current year	8,524			5,143
Net reserve for losses and LAE at end of year	46,850			28,142
Plus: Reinsurance recoverables	—			—
Reserve for losses and LAE at end of year	$	46,850		$	28,142

Loans in default at end of year	4,783			1,757



($ in thousands)	Incurred Loss and Allocated LAE, For the Years Ended December 31,																As of December 31, 2017
Accident Year	2010 Unaudited		2011 Unaudited		2012 Unaudited		2013 Unaudited		2014 Unaudited		2015 Unaudited		2016 Unaudited		2017		Total of IBNR plus Expected Development on Reported Defaults		Cumulative Number of Reported Defaults (1)
2010	$	—	$	—	$	—	$	—	$	—	$	—	$	—	$	—	$	—	—
2011			57		—		—		—		—		—		—		—		1
2012					1,523		858		814		781		748		809		—		19
2013							2,986		2,461		2,008		1,997		2,060		12		52
2014									6,877		4,312		3,323		2,984		14		98
2015											14,956		9,625		8,893		134		238
2016													21,889		11,890		482		388
2017															38,178		2,573		4,494
Total															$	64,814

(1) Cumulative number of reported defaults includes cumulative paid claims plus loans in default by accident year as of December 31, 2017.



($ in thousands)	Cumulative Paid Losses and Allocated LAE For the Years Ended December 31,
Accident Year	2010 Unaudited		2011 Unaudited		2012 Unaudited		2013 Unaudited		2014 Unaudited		2015 Unaudited		2016 Unaudited		2017
2010	$	—	$	—	$	—	$	—	$	—	$	—	$	—	—
2011			—		—		—		—		—		—		—
2012					24		535		659		665		665		808
2013							239		928		1,501		1,775		1,880
2014									138		1,587		2,463		2,787
2015											544		3,610		6,960
2016													927		4,896
2017															633
Total															$	17,964
All outstanding liabilities before 2010, net of reinsurance															—
Reserve for losses and LAE, net of reinsurance															$	46,850

For our mortgage insurance portfolio, our average annual payout of losses as of December 31, 2017 is as follows:



Average Annual Percentage Payout of Incurred Losses and Allocated LAE by Year
Year	1		2		3		4		5		6

Average Payout	6	%	43	%	28	%	8	%	3	%	18	%

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Schedule of future minimum lease payments of all non-cancelable operating leases

The future minimum lease payments of non-cancelable operating leases are as follows at December 31, 2017:



Year Ended December 31 (In thousands)
2018	$	2,479
2019	2,649
2020	2,594
2021	2,651
2022	2,710
2023 and thereafter	4,517
Total minimum payments required	$	17,600

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of portion of nonvested Common Shares earned based upon achievement of compounded annual book value per share growth

The portion of the nonvested performance-based share awards that will be earned based upon the achievement of compounded annual book value per share growth is as follows:



	2017 Performance-Based Grants				2016 Performance-Based Grants				2013, 2014 and 2015 Performance-Based Grants
Performance level	Compounded Annual Book Value Per Share Growth		Nonvested Common Shares Earned		Compounded Annual Book Value Per Share Growth		Nonvested Common Shares Earned		Compounded Annual Book Value Per Share Growth		Nonvested Common Shares Earned
	<16	%	0	%	<13	%	0	%	<11	%	0	%
Threshold	16	%	25	%	13	%	25	%	11	%	10	%
	17	%	50	%	14	%	50	%	12	%	36	%
	18	%	75	%	15	%	75	%	13	%	61	%
									14	%	87	%
Maximum	≥19	%	100	%	≥16	%	100	%	≥15	%	100	%

Summary of nonvested Common Share and nonvested Common Share unit activity

The following tables summarize nonvested Common Share and nonvested Common Share unit activity for the year ended December 31:



	2017
	Time and Performance- Based Share Awards				Time-Based Share Awards				Share Units
(Shares in thousands)	Number of Shares		Weighted Average Grant Date Fair Value		Number of Shares		Weighted Average Grant Date Fair Value		Number of Share Units		Weighted Average Grant Date Fair Value
Outstanding at beginning of year	1,503		$	15.41	605		$	16.32	493		$	19.24
Granted	140		36.29		91		36.29		387		33.40
Vested	(48	)	22.48		(286	)	15.74		(321	)	19.00
Forfeited	—		N/A		—		N/A		(23	)	30.49
Outstanding at end of year	1,595		$	17.03	410		$	21.12	536		$	29.13



	2016
	Time and Performance- Based Share Awards			Time-Based Share Awards				Share Units
(Shares in thousands)	Number of Shares	Weighted Average Grant Date Fair Value		Number of Shares		Weighted Average Grant Date Fair Value		Number of Share Units		Weighted Average Grant Date Fair Value
Outstanding at beginning of year	1,294	$	15.15	890		$	12.31	544		$	19.84
Granted	209	17.01		181		17.01		215		18.21
Vested	—	N/A		(461	)	9.04		(254	)	19.71
Forfeited	—	N/A		(5	)	0.23		(12	)	18.12
Outstanding at end of year	1,503	$	15.41	605		$	16.32	493		$	19.24



	2015
	Time and Performance- Based Share Awards				Time-Based Share Awards				Share Units
(Shares in thousands)	Number of Shares		Weighted Average Grant Date Fair Value		Number of Shares		Weighted Average Grant Date Fair Value		Number of Share Units		Weighted Average Grant Date Fair Value
Outstanding at beginning of year	1,290		$	14.83	1,472		$	9.04	664		$	18.32
Granted	50		24.58		109		24.51		129		24.47
Vested	—		N/A		(644	)	6.67		(239	)	18.18
Forfeited	(46	)	16.40		(47	)	15.50		(10	)	17.89
Outstanding at end of year	1,294		$	15.15	890		$	12.31	544		$	19.84

Schedule of compensation expense, net of forfeitures, and related tax effects recognized in connection with nonvested shares

Compensation expense, net of forfeitures, and related tax effects recognized in connection with nonvested shares were as follows for the years ended December 31:



(In thousands)	2017		2016		2015
Compensation expense	$	18,688	$	16,881	$	13,633
Income tax benefit	6,017		5,455		4,378

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Schedule of components of income tax expense

Income tax expense consists of the following components for the years ended December 31:



(In thousands)	2017			2016		2015
Current	$	38,252		$	31,712	$	18,910
Deferred	65,660			57,564		52,157
Remeasurement of net deferred tax liability for enacted changes in tax law	(85,091		)	—		—
Total income tax expense	$	18,821		$	89,276	$	71,067

Schedule of reconciliation of difference between income tax expense and expected tax provision at weighted average tax rate

The reconciliation of the difference between income tax expense and the expected tax provision at the weighted average tax rate was as follows for the years ended December 31:



($ in thousands)	2017			% of pretax income		2016			% of pretax income		2015			% of pretax income
Tax provision at weighted average statutory rates	$	109,309		27.4	%	$	91,092		29.2	%	$	72,461		31.7	%
Change in valuation of net deferred tax liability	(85,091		)	(21.3	)	—			—		—			—
Excess tax benefits from stock-based compensation	(3,227		)	(0.8	)	—			—		—			—
Tax exempt interest, net of proration	(2,608		)	(0.7	)	(2,181		)	(0.7	)	(1,741		)	(0.8	)
Non-deductible expenses	392			0.1		378			0.1		381			0.2
Other	46			0.0		(13		)	0.0		(34		)	0.0
Total income tax expense	$	18,821		4.7	%	$	89,276		28.6	%	$	71,067		31.1	%

Schedule of net deferred tax (liability) asset and components

The net deferred tax liability was comprised of the following at December 31:



(In thousands)	2017			2016
Deferred tax assets	$	28,696		$	43,291
Deferred tax liabilities	(156,332		)	(185,878		)
Net deferred tax liability	$	(127,636	)	$	(142,587	)

The components of the net deferred tax liability were as follows at December 31:



(In thousands)	2017			2016
Contingency reserves	$	(151,586	)	$	(181,031	)
Unearned premium reserve	14,454			19,722
Nonvested shares	6,442			8,445
Deferred policy acquisition costs	(3,224		)	(4,690		)
Unearned ceding commissions	2,815			3,568
Fixed assets	2,529			4,702
Start-up expenditures, net	1,951			3,705
Unrealized (gain) loss on investments	(1,403		)	2,181
Accrued expenses	335			775
Loss reserves	158			170
Prepaid expenses	(119		)	(157		)
Organizational expenditures	12			23
Net deferred tax liability	$	(127,636	)	$	(142,587	)

Earnings per Share (EPS) (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Schedule of reconciliation of net income and weighted average common shares outstanding used in computations of basic and diluted earnings per common share



(In thousands, except per share amounts)	2017		2016		2015
Net income	$	379,747	$	222,606	$	157,331
Less: Common Shares dividends declared	—		—		—
Undistributed net income	$	379,747	$	222,606	$	157,331
Net income allocable to Common	$	379,747	$	222,606	$	157,331

Basic earnings per share	$	4.07	$	2.45	$	1.74
Diluted earnings per share	$	3.99	$	2.41	$	1.72
Basic weighted average Common Shares outstanding	93,330		90,913		90,351
Dilutive effect of nonvested shares	1,881		1,332		1,387
Diluted weighted average Common Shares outstanding	95,211		92,245		91,738

Accumulated Other Comprehensive Income (Loss) (Tables)

12 Months Ended

Dec. 31, 2017

Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]

Rollforward of accumulated other comprehensive income (loss)

The following table shows the rollforward of accumulated other comprehensive income (loss) for the year ended December 31:



	2017
(In thousands)	Before Tax			Tax Effect			Net of Tax
Balance at beginning of year	$	(14,436	)	$	2,181		$	(12,255	)
Other comprehensive income (loss):
Unrealized holding gains (losses) on investments:
Unrealized holding gains arising during the period	14,602			(5,239		)	9,363
Less: Reclassification adjustment for gains included in net income (1)	(2,015		)	720			(1,295		)
Net unrealized gains on investments	12,587			(4,519		)	8,068
Other comprehensive income	12,587			(4,519		)	8,068
Reclassification of certain income tax effects resulting from tax reform	—			935			935
Balance at end of year	$	(1,849	)	$	(1,403	)	$	(3,252	)



	2016
(In thousands)	Before Tax			Tax Effect			Net of Tax
Balance at beginning of year	$	661		$	(760	)	$	(99	)
Other comprehensive income (loss):
Unrealized holding gains (losses) on investments:
Unrealized holding losses arising during the period	(13,156		)	2,376			(10,780		)
Less: Reclassification adjustment for gains included in net income (1)	(1,941		)	565			(1,376		)
Net unrealized losses on investments	(15,097		)	2,941			(12,156		)
Other comprehensive loss	(15,097		)	2,941			(12,156		)
Balance at end of year	$	(14,436	)	$	2,181		$	(12,255	)

_______________________________________________________________________________


(1)	Included in net realized investments gains on our consolidated statements of comprehensive income.

Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Schedule of assets and liabilities measured at fair vale on a recurring basis



December 31, 2017 (In thousands)	Quoted Prices in Active Markets for Identical Instruments (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Recurring fair value measurements
Financial Assets:
U.S. Treasury securities	$	227,805	$	—	$	—	$	227,805
U.S. agency securities	—		33,114		—		33,114
U.S. agency mortgage-backed securities	—		456,037		—		456,037
Municipal debt securities	—		465,255		—		465,255
Corporate debt securities	—		611,728		—		611,728
Residential and commercial mortgage securities	—		79,407		—		79,407
Asset-backed securities	—		167,922		—		167,922
Money market funds	263,797		—		—		263,797
Total assets at fair value	$	491,602	$	1,813,463	$	—	$	2,305,065



December 31, 2016 (In thousands)	Quoted Prices in Active Markets for Identical Instruments (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Recurring fair value measurements
Financial Assets:
U.S. Treasury securities	$	191,548	$	—	$	—	$	191,548
U.S. agency securities	—		18,441		—		18,441
U.S. agency mortgage-backed securities	—		316,494		—		316,494
Municipal debt securities	—		334,324		—		334,324
Corporate debt securities	—		456,357		—		456,357
Residential and commercial mortgage securities	—		68,336		—		68,336
Asset-backed securities	—		127,172		—		127,172
Money market funds	102,430		—		—		102,430
Total assets at fair value	$	293,978	$	1,321,124	$	—	$	1,615,102

Schedule of changes during period in Level 3 liabilities measured at fair value on a recurring basis, and realized and unrealized losses (gains) related to Level 3 liabilities



	Year Ended December 31,
(In thousands)	2017		2016
Level 3 Liabilities
Fair value of derivative liabilities at beginning of period	$	—	$	1,232
Net realized and unrealized losses (gains) included in income	—		(1,934		)
Other comprehensive (income) loss	—		—
Purchases, sales, issues and settlements, net	—		702
Gross transfers in	—		—
Gross transfers out	—		—
Fair value of derivative liabilities at end of period	$	—	$	—

Changes in net unrealized losses (gains) included in income on instruments held at end of period	$	—	$	(1,934	)

Statutory Accounting (Tables)

12 Months Ended

Dec. 31, 2017

Insurance [Abstract]

Schedule of statutory net income, statutory surplus and contingency reserve liability

The following table presents Essent Guaranty’s and Essent PA’s statutory net income, statutory surplus and contingency reserve liability as of and for the years ended December 31:



(In thousands)	2017		2016		2015
Essent Guaranty
Statutory net income	$	261,811	$	215,951	$	172,688
Statutory surplus	761,006		578,887		522,172
Contingency reserve liability	678,701		480,829		315,058

Essent PA
Statutory net income	$	10,250	$	12,978	$	15,200
Statutory surplus	45,509		47,387		47,139
Contingency reserve liability	43,141		36,401		27,502

- Definition

Tabular disclosure of how the entity's reporting under GAAP as of the balance sheet date differs from the results based on prescribed and permitted accounting practices of the state or country of domicile in which a relevant statutory filing is made, or differences in results based on the National Association of Insurance Commissioners (NAIC) prescribed practices, or a combination thereof. Describes the accounting practices used and the related monetary effect on statutory surplus, net income, and risk-based capital. If an insurance enterprise's risk-based capital would have triggered a regulatory event had it not used a permitted practice, that fact is disclosed in the financial statements. Permitted statutory accounting practices include practices not prescribed but allowed by the domiciliary state insurance department regulatory authority.

+ References + Details

Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Summary of unaudited quarterly results of operations



	2017
(In thousands, except per share amounts)	December 31		September 30		June 30		March 31
Net premiums earned	$	147,976	$	137,940	$	126,563	$	117,651
Other revenues	13,134		12,263		11,043		9,941
Provision for losses and LAE	17,456		4,313		1,770		3,693
Other underwriting and operating expenses	36,480		37,035		35,686		36,332
Interest expense	1,817		1,456		1,189		716
Income before income taxes	105,357		107,399		98,961		86,851
Net income	162,638		78,393		72,118		66,598
Basic earnings per Common Share	$	1.69	$	0.83	$	0.79	$	0.73
Diluted earnings per Common Share	$	1.65	$	0.82	$	0.77	$	0.72
Basic weighted average Common Shares outstanding	96,429		94,185		91,381		91,258
Diluted weighted average Common Shares outstanding	98,497		96,094		93,162		93,023



	2016
(In thousands, except per share amounts)	December 31		September 30		June 30		March 31
Net premiums earned	$	116,792	$	110,801	$	100,711	$	94,403
Other revenues	9,581		10,453		7,454		8,063
Provision for losses and LAE	3,865		4,965		2,964		3,731
Other underwriting and operating expenses	34,836		32,792		31,409		31,388
Interest expense	370		56		—		—
Income before income taxes	87,302		83,441		73,792		67,347
Net income	62,686		59,711		52,258		47,951
Basic earnings per Common Share	$	0.69	$	0.66	$	0.57	$	0.53
Diluted earnings per Common Share	$	0.68	$	0.65	$	0.57	$	0.52
Basic weighted average Common Shares outstanding	90,991		90,961		90,912		90,785
Diluted weighted average Common Shares outstanding	92,577		92,399		92,138		91,859

Nature of Operations and Basis of Presentation (Details)	12 Months Ended
	Dec. 31, 2017 state
Essent Guaranty
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of states in which the entity is licensed to write mortgage insurance	50
Affiliated Entity \| Essent Re \| Quota share reinsurance
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reinsurance percentage	25.00%
Affiliated Entity \| Essent PA \| Reinsurance for mortgage insurance coverage in excess of 25%
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reinsurance for mortgage insurance coverage threshold (as a percent)	25.00%
Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Residential mortgage down payment percentage for which mortgage insurance is generally required (percent) (less than)	20.00%

Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Long-Lived Assets
Cost	$ 57,445	$ 54,662
Accumulated Depreciation/ Amortization	$ (50,466)	(46,543)
Furniture and fixtures
Long-Lived Assets
Estimated useful lives (in years)	5 years
Cost	$ 2,074	2,042
Accumulated Depreciation/ Amortization	$ (1,592)	(1,298)
Equipment, computer hardware and purchased software \| Minimum
Long-Lived Assets
Estimated useful lives (in years)	2 years
Equipment, computer hardware and purchased software \| Maximum
Long-Lived Assets
Estimated useful lives (in years)	3 years
Office equipment
Long-Lived Assets
Cost	$ 640	625
Accumulated Depreciation/ Amortization	(602)	(513)
Computer hardware
Long-Lived Assets
Cost	6,837	5,700
Accumulated Depreciation/ Amortization	(5,413)	(4,260)
Purchased software
Long-Lived Assets
Cost	35,710	35,148
Accumulated Depreciation/ Amortization	$ (34,620)	(33,304)
Costs of internal-use software
Long-Lived Assets
Estimated useful lives (in years)	3 years
Cost	$ 7,965	7,140
Accumulated Depreciation/ Amortization	(6,773)	(6,075)
Leasehold improvements
Long-Lived Assets
Cost	4,219	4,007
Accumulated Depreciation/ Amortization	$ (1,466)	$ (1,093)

Summary of Significant Accounting Policies (Details 2) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Policy Acquisition Costs
Policy acquisition costs deferred	$ 8.0	$ 7.7	$ 6.6
Other underwriting and operating expenses
Deferred Policy Acquisition Costs
Amortization of deferred policy acquisition costs	$ 6.0	$ 5.8	$ 4.7

Summary of Significant Accounting Policies (Details 3) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Insurance Premium Revenue Recognition
Earned premiums from mortgage guaranty insurance monthly policies as a percentage of total earned premiums (percent)	86.00%
Threshold coverage period for single premium primary mortgage insurance policies (in years)	1 year
Unearned single premium recognized as earned upon notice of policy cancellation due to repayment of insured loan by borrower	$ 23.2	$ 36.9

Summary of Significant Accounting Policies (Details 4)	12 Months Ended
Summary of Significant Accounting Policies (Details 4)	Dec. 31, 2017 USD ($) payment	Dec. 31, 2016 USD ($)
Reserve for Losses and Loss Adjustment Expenses
Number of consecutive missed loan payments by borrower for classification of insured loan as in default \| payment	2
Premium Deficiency Reserve
Premium deficiency reserve \| $	$ 0	$ 0

Summary of Significant Accounting Policies (Details 5) - USD ($) $ in Thousands	Jan. 01, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption		$ (39)
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption		$ 72
Accounting Standards Update 2016-09 \| Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption	$ 100

Summary of Significant Accounting Policies (Details 6) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Accounting Standard Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of certain income tax effects resulting from tax reform	$ 0.9

Investments Available for Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Investments available for sale
Amortized Cost	$ 2,306,914	$ 1,629,538
Unrealized Gains	15,174	7,130
Unrealized Losses	(17,023)	(21,566)
Fair Value	2,305,065	1,615,102
U.S. Treasury securities
Investments available for sale
Amortized Cost	231,905	195,990
Unrealized Gains	2	55
Unrealized Losses	(4,102)	(4,497)
Fair Value	227,805	191,548
Municipal debt securities
Investments available for sale
Amortized Cost	457,418	334,048
Unrealized Gains	9,098	3,649
Unrealized Losses	(1,261)	(3,373)
Fair Value	465,255	334,324
Corporate debt securities
Investments available for sale
Amortized Cost	610,516	457,842
Unrealized Gains	4,249	2,343
Unrealized Losses	(3,037)	(3,828)
Fair Value	611,728	456,357
Residential and commercial mortgage securities
Investments available for sale
Amortized Cost	78,974	68,430
Unrealized Gains	791	488
Unrealized Losses	(358)	(582)
Fair Value	79,407	68,336
Asset-backed securities
Investments available for sale
Amortized Cost	167,638	127,359
Unrealized Gains	467	260
Unrealized Losses	(183)	(447)
Fair Value	167,922	127,172
Money market funds
Investments available for sale
Amortized Cost	263,808	102,430
Unrealized Gains	0	0
Unrealized Losses	(11)	0
Fair Value	263,797	102,430
U.S. Agency \| U.S. agency securities
Investments available for sale
Amortized Cost	33,669	18,785
Unrealized Gains	0	0
Unrealized Losses	(555)	(344)
Fair Value	33,114	18,441
U.S. Agency \| U.S. agency mortgage-backed securities
Investments available for sale
Amortized Cost	462,986	324,654
Unrealized Gains	567	335
Unrealized Losses	(7,516)	(8,495)
Fair Value	$ 456,037	$ 316,494

Investments Available for Sale (Details 2)	Dec. 31, 2017	Dec. 31, 2016
Municipal debt securities
Investments available for sale
Percentage of debt securities	100.00%	100.00%
Corporate debt securities
Investments available for sale
Percentage of debt securities	100.00%	100.00%
Financial \| Corporate debt securities
Investments available for sale
Percentage of debt securities	45.90%	40.60%
Consumer, non-cyclical \| Corporate debt securities
Investments available for sale
Percentage of debt securities	16.20%	18.60%
Energy \| Corporate debt securities
Investments available for sale
Percentage of debt securities	7.80%	9.30%
Communications \| Corporate debt securities
Investments available for sale
Percentage of debt securities	7.30%	6.00%
Industrial \| Corporate debt securities
Investments available for sale
Percentage of debt securities	6.30%	5.60%
Consumer, cyclical \| Corporate debt securities
Investments available for sale
Percentage of debt securities	5.30%	6.30%
Utilities \| Corporate debt securities
Investments available for sale
Percentage of debt securities	5.30%	6.00%
Technology \| Corporate debt securities
Investments available for sale
Percentage of debt securities	3.90%	4.30%
Basic materials \| Corporate debt securities
Investments available for sale
Percentage of debt securities	2.00%	3.30%
Special revenue bonds \| Municipal debt securities
Investments available for sale
Percentage of debt securities	63.60%	63.60%
General obligation bonds \| Municipal debt securities
Investments available for sale
Percentage of debt securities	30.70%	29.70%
Certificate of participation bonds \| Municipal debt securities
Investments available for sale
Percentage of debt securities	4.40%	4.90%
Tax allocation bonds \| Municipal debt securities
Investments available for sale
Percentage of debt securities	0.80%	1.10%
Special tax bonds \| Municipal debt securities
Investments available for sale
Percentage of debt securities	0.50%	0.70%

Investments Available for Sale (Details 3) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Amortized Cost
Total amortized investment	$ 2,306,914	$ 1,629,538
Fair Value
Fair Value	2,305,065	1,615,102
U.S. Treasury securities
Amortized Cost
Due in 1 year	58,429
Due after 1 but within 5 years	72,469
Due after 5 but within 10 years	71,006
Due after 10 years	30,001
Subtotal	231,905
Total amortized investment	231,905	195,990
Fair Value
Due in 1 year	58,411
Due after 1 but within 5 years	71,661
Due after 5 but within 10 years	68,376
Due after 10 years	29,357
Subtotal	227,805
Fair Value	227,805	191,548
Municipal debt securities
Amortized Cost
Due in 1 year	33,038
Due after 1 but within 5 years	97,637
Due after 5 but within 10 years	179,245
Due after 10 years	147,498
Subtotal	457,418
Total amortized investment	457,418	334,048
Fair Value
Due in 1 year	32,998
Due after 1 but within 5 years	97,831
Due after 5 but within 10 years	183,610
Due after 10 years	150,816
Subtotal	465,255
Fair Value	465,255	334,324
Corporate debt securities
Amortized Cost
Due in 1 year	80,177
Due after 1 but within 5 years	332,105
Due after 5 but within 10 years	196,289
Due after 10 years	1,945
Subtotal	610,516
Total amortized investment	610,516	457,842
Fair Value
Due in 1 year	80,093
Due after 1 but within 5 years	331,790
Due after 5 but within 10 years	197,848
Due after 10 years	1,997
Subtotal	611,728
Fair Value	611,728	456,357
Residential and commercial mortgage securities
Amortized Cost
Total amortized investment	78,974	68,430
Fair Value
Fair Value	79,407	68,336
Asset-backed securities
Amortized Cost
Total amortized investment	167,638	127,359
Fair Value
Fair Value	167,922	127,172
Money market funds
Amortized Cost
Total amortized investment	263,808	102,430
Fair Value
Fair Value	263,797	102,430
U.S. Agency \| U.S. agency securities
Amortized Cost
Due in 1 year	0
Due after 1 but within 5 years	33,669
Subtotal	33,669
Total amortized investment	33,669	18,785
Fair Value
Due in 1 year	0
Due after 1 but within 5 years	33,114
Subtotal	33,114
Fair Value	33,114	18,441
U.S. Agency \| U.S. agency mortgage-backed securities
Amortized Cost
Total amortized investment	462,986	324,654
Fair Value
Fair Value	$ 456,037	$ 316,494

Investments Available for Sale (Details 4) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Realized gross gains and losses on the sale of investments available for sale
Realized gross gains	$ 2,504	$ 2,822	$ 3,908
Realized gross losses	425	788	1,073
Fair Value
Less than 12 months	835,553	877,394
12 months or more	432,761	77,782
Total	1,268,314	955,176
Gross Unrealized Losses
Less than 12 months	(5,177)	(20,789)
12 months or more	(11,846)	(777)
Total	(17,023)	(21,566)
Other information
Other-than-temporary impairments	100	100	$ 300
Fair value of investments deposited with insurance regulatory authorities	8,600	8,500
U.S. Treasury securities
Fair Value
Less than 12 months	151,119	160,018
12 months or more	69,454	0
Total	220,573	160,018
Gross Unrealized Losses
Less than 12 months	(1,240)	(4,497)
12 months or more	(2,862)	0
Total	(4,102)	(4,497)
Municipal debt securities
Fair Value
Less than 12 months	124,171	149,368
12 months or more	23,492	6,015
Total	147,663	155,383
Gross Unrealized Losses
Less than 12 months	(817)	(3,351)
12 months or more	(444)	(22)
Total	(1,261)	(3,373)
Corporate debt securities
Fair Value
Less than 12 months	214,371	213,965
12 months or more	94,261	8,344
Total	308,632	222,309
Gross Unrealized Losses
Less than 12 months	(1,213)	(3,704)
12 months or more	(1,824)	(124)
Total	(3,037)	(3,828)
Residential and commercial mortgage securities
Fair Value
Less than 12 months	29,842	18,026
12 months or more	5,988	14,014
Total	35,830	32,040
Gross Unrealized Losses
Less than 12 months	(179)	(434)
12 months or more	(179)	(148)
Total	(358)	(582)
Asset-backed securities
Fair Value
Less than 12 months	58,798	28,294
12 months or more	5,828	47,597
Total	64,626	75,891
Gross Unrealized Losses
Less than 12 months	(133)	(57)
12 months or more	(50)	(390)
Total	(183)	(447)
Money market funds
Fair Value
Less than 12 months	59,489
12 months or more	0
Total	59,489
Gross Unrealized Losses
Less than 12 months	(11)
12 months or more	0
Total	(11)
Essent Re
Other information
Fair value of the required investments on deposit in trusts	615,800	349,600
U.S. Agency \| U.S. agency securities
Fair Value
Less than 12 months	17,320	18,441
12 months or more	15,794	0
Total	33,114	18,441
Gross Unrealized Losses
Less than 12 months	(190)	(344)
12 months or more	(365)	0
Total	(555)	(344)
U.S. Agency \| U.S. agency mortgage-backed securities
Fair Value
Less than 12 months	180,443	289,282
12 months or more	217,944	1,812
Total	398,387	291,094
Gross Unrealized Losses
Less than 12 months	(1,394)	(8,402)
12 months or more	(6,122)	(93)
Total	$ (7,516)	$ (8,495)

Investments Available for Sale (Details 5) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Components of net investment income
Gross investment income	$ 42,954	$ 30,007	$ 21,756
Investment expenses	(2,728)	(2,117)	(1,871)
Net investment income	40,226	27,890	19,885
Fixed maturities
Components of net investment income
Gross investment income	41,935	29,865	21,693
Short-term investments
Components of net investment income
Gross investment income	$ 1,019	$ 142	$ 63

Accounts Receivable (Details) - USD ($)	12 Months Ended
Accounts Receivable (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Accounts Receivable
Premiums receivable	$ 29,027,000	$ 21,265,000
Other receivables	725,000	367,000
Total accounts receivable	29,752,000	21,632,000
Less: Allowance for doubtful accounts	0	0
Accounts receivable, net	29,752,000	21,632,000
Provision for doubtful accounts	$ 0	$ 0
Premiums receivable
Accounts Receivable
Threshold period unpaid for write-off of mortgage insurance premiums	90 days

Triad Transaction (Details) - USD ($)	12 Months Ended
Triad Transaction (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 01, 2009
Services Agreement \| Triad \| Other income
Services agreement
Fees earned under Services Agreement	$ 1,100,000	$ 1,400,000	$ 1,800,000
Essent Guaranty \| Triad Assets
Triad Transaction
Contingent payments				$ 15,000,000
Essent Guaranty \| Triad Assets \| Fixed payment purchase price obligation
Triad Transaction
Payment obligation				$ 15,000,000

Reserve for Losses and Loss Adjustment Expenses (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) loan	Dec. 31, 2016 USD ($) loan	Dec. 31, 2015 USD ($)
Reconciliation of the beginning and ending reserve balances for losses and loss adjustment expenses (LAE)
Reserve for losses and LAE at beginning of year	$ 28,142	$ 17,760
Less: Reinsurance recoverables	0	0	$ 0
Net reserve for losses and LAE at beginning of year	28,142	17,760
Add provision for losses and LAE, net of reinsurance, occurring in:
Current year	38,178	21,889
Prior years	(10,946)	(6,364)
Net incurred losses during the current year	27,232	15,525	11,905
Deduct payments for losses and LAE, net of reinsurance, occurring in:
Current year	633	927
Prior years	7,891	4,216
Net loss and LAE payments during the current year	8,524	5,143
Net reserve for losses and LAE at end of year	46,850	28,142	17,760
Plus: Reinsurance recoverables	0	0	0
Reserve for losses and LAE at end of year	$ 46,850	$ 28,142	$ 17,760
Loans in default at end of year \| loan	4,783	1,757

Reserve for Losses and Loss Adjustment Expenses (Details 2) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) loan	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Liability for Future Policy Benefits and Unpaid Claims and Claims Adjustment Expense [Abstract]
Incurred claims and claim adjustment expenses	$ 7,891	$ 4,216
Favorable prior year development	10,946	6,364
Reserve for losses and LAE, for prior years	$ 9,300	7,200
Number of loans in default increase (decrease) during period \| loan	3,026
Number of loans in hurricane impacted areas in default increase (decrease) during period \| loan	2,288
Liability for Claims and Claims Adjustment Expense [Line Items]
Reserve for losses and defaults	$ 46,850	$ 28,142	$ 17,760
Hurricane
Liability for Claims and Claims Adjustment Expense [Line Items]
Reserve for losses and defaults	$ 11,100

Reserve for Losses and Loss Adjustment Expenses (Details 3) $ in Thousands	Dec. 31, 2017 USD ($) loan	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)
Liability for Claims and Claims Adjustment Expense [Line Items]
All outstanding liabilities before 2010, net of reinsurance	$ 0
Reserve for losses and LAE, net of reinsurance	46,850	$ 28,142	$ 17,760
Property Insurance Product Line
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Loss and Allocated LAE, For the Years Ended December 31,	64,814
Cumulative Paid Losses and Allocated LAE For the Years Ended December 31,	17,964
2010 \| Property Insurance Product Line
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Loss and Allocated LAE, For the Years Ended December 31,	0	0	0	$ 0	$ 0	$ 0	$ 0	$ 0
Total of IBNR plus Expected Development on Reported Defaults	$ 0
Cumulative Number of Reported Defaults \| loan	0
Cumulative Paid Losses and Allocated LAE For the Years Ended December 31,	$ 0	0	0	0	0	0	0	$ 0
2011 \| Property Insurance Product Line
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Loss and Allocated LAE, For the Years Ended December 31,	0	0	0	0	0	0	57
Total of IBNR plus Expected Development on Reported Defaults	$ 0
Cumulative Number of Reported Defaults \| loan	1
Cumulative Paid Losses and Allocated LAE For the Years Ended December 31,	$ 0	0	0	0	0	0	$ 0
2012 \| Property Insurance Product Line
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Loss and Allocated LAE, For the Years Ended December 31,	809	748	781	814	858	1,523
Total of IBNR plus Expected Development on Reported Defaults	$ 0
Cumulative Number of Reported Defaults \| loan	19
Cumulative Paid Losses and Allocated LAE For the Years Ended December 31,	$ 808	665	665	659	535	$ 24
2013 \| Property Insurance Product Line
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Loss and Allocated LAE, For the Years Ended December 31,	2,060	1,997	2,008	2,461	2,986
Total of IBNR plus Expected Development on Reported Defaults	$ 12
Cumulative Number of Reported Defaults \| loan	52
Cumulative Paid Losses and Allocated LAE For the Years Ended December 31,	$ 1,880	1,775	1,501	928	$ 239
2014 \| Property Insurance Product Line
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Loss and Allocated LAE, For the Years Ended December 31,	2,984	3,323	4,312	6,877
Total of IBNR plus Expected Development on Reported Defaults	$ 14
Cumulative Number of Reported Defaults \| loan	98
Cumulative Paid Losses and Allocated LAE For the Years Ended December 31,	$ 2,787	2,463	1,587	$ 138
2015 \| Property Insurance Product Line
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Loss and Allocated LAE, For the Years Ended December 31,	8,893	9,625	14,956
Total of IBNR plus Expected Development on Reported Defaults	$ 134
Cumulative Number of Reported Defaults \| loan	238
Cumulative Paid Losses and Allocated LAE For the Years Ended December 31,	$ 6,960	3,610	$ 544
2016 \| Property Insurance Product Line
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Loss and Allocated LAE, For the Years Ended December 31,	11,890	21,889
Total of IBNR plus Expected Development on Reported Defaults	$ 482
Cumulative Number of Reported Defaults \| loan	388
Cumulative Paid Losses and Allocated LAE For the Years Ended December 31,	$ 4,896	$ 927
2017 \| Property Insurance Product Line
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Loss and Allocated LAE, For the Years Ended December 31,	38,178
Total of IBNR plus Expected Development on Reported Defaults	$ 2,573
Cumulative Number of Reported Defaults \| loan	4,494
Cumulative Paid Losses and Allocated LAE For the Years Ended December 31,	$ 633

Reserve for Losses and Loss Adjustment Expenses (Details 4) - Property Insurance Product Line	Dec. 31, 2017
Average Annual Percentage Payout of Incurred Losses and Allocated LAE by Year
Year 1	6.00%
Year 2	43.00%
Year 3	28.00%
Year 4	8.00%
Year 5	3.00%
Year 6	18.00%

Debt Obligations (Details) - USD ($)			12 Months Ended
Debt Obligations (Details) - USD ($)	May 17, 2017	Apr. 19, 2016	Dec. 31, 2017	Dec. 31, 2016
Credit Facility [Line Items]
Credit facility, maximum borrowing capacity	$ 375,000,000
Credit facility borrowings			$ 248,591,000	$ 100,000,000
Revolving Credit Facility
Credit Facility [Line Items]
Credit facility, term	4 years	3 years
Credit facility, maximum borrowing capacity	$ 250,000,000	$ 200,000,000
Credit facility, commitment fee rate			0.35%
Credit facility borrowings			$ 250,000,000	$ 100,000,000
Weighted average interest rate during period			3.49%	2.73%
Term Loan
Credit Facility [Line Items]
Credit facility, maximum borrowing capacity	125,000,000
Uncommitted Line
Credit Facility [Line Items]
Credit facility, maximum borrowing capacity	$ 75,000,000

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References + Details

Commitments and Contingencies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Indemnifications related to contract underwriting services
Loss Contingencies [Line Items]
Amount paid for remedies	$ 0.2	$ 0.1

Commitments and Contingencies (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Rent expense	$ 2,100	$ 1,900	$ 1,900
Future minimum lease payments of all non-cancelable operating leases
2018	2,479
2019	2,649
2020	2,594
2021	2,651
2022	2,710
2023 and thereafter	4,517
Total minimum payments required	17,600
Minimum sublease rental income, due in 2018	$ 100

Capital Stock (Details) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
Capital Stock (Details) $ / shares in Units, $ in Thousands	Aug. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) vote shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($)
Capital [Abstract]
Authorized share capital (in shares) \| shares		233,333,000	233,333,000
Number of votes per share		1
Shareholder ownership threshold for voting rights (as a percent)		9.50%
Maximum number of votes per share for certain shareholders under 9.5% shareholder provision		1
Minimum number of votes per share for other shareholders under 9.5% shareholder provision		1
Common Shares, issued (in shares) \| shares	5,000,000.0	98,434,000	93,105,000
Share price (in dollars per share) \| $ / shares	$ 39.90
Net proceeds from sale of stock \| $	$ 197,700	$ 197,829	$ 0	$ (537)

Stock-Based Compensation (Details) - USD ($) $ in Millions	1 Months Ended										12 Months Ended
Stock-Based Compensation (Details) - USD ($) $ in Millions	Feb. 20, 2018	May 31, 2017	Feb. 28, 2017	Jan. 31, 2017	May 31, 2016	Feb. 29, 2016	May 31, 2015	Feb. 28, 2015	Feb. 28, 2014	Sep. 30, 2013	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	May 03, 2017	May 02, 2017	Dec. 31, 2014
Stock-based compensation
Nonvested shares outstanding (in shares)														2,600,000
Shares tendered by employees to pay employee withholding taxes (in shares)											223,027	184,583	201,553
Nonvested shares
Stock-based compensation
Total fair value of shares vested											$ 22.4	$ 15.6	$ 22.4
Total unrecognized compensation expense											$ 18.4
Expected weighted average period for recognition of expense											1 year 9 months 29 days
Nonvested share units
Stock-based compensation
Nonvested shares outstanding (in shares)											536,000	493,000	544,000			664,000
Granted (in shares)											387,000	215,000	129,000
Time-Based Share Awards \| Nonvested shares
Stock-based compensation
Nonvested shares outstanding (in shares)											410,000	605,000	890,000			1,472,000
Granted (in shares)											91,000	181,000	109,000
2013 Plan
Stock-based compensation
Shares authorized (in shares)														7,500,000.0	14,700,000
Number of share available for future grant (in shares)											4,900,000
First Anniversary Of Completion Of Performance Period Vesting \| 2013 Plan \| Vesting Based On Performance \| Nonvested shares
Stock-based compensation
Vesting period										1 year
Certain Senior Management \| 2013 Plan \| Time-Based Share Awards \| Nonvested shares
Stock-based compensation
Vesting period			3 years			3 years		3 years	3 years	4 years
Certain Senior Management \| 2013 Plan \| Vesting Based On Performance \| Nonvested shares
Stock-based compensation
Performance period			3 years			3 years		3 years	3 years	3 years
Certain Senior Management \| Vesting period one \| 2013 Plan \| Time-Based Share Awards \| Nonvested shares
Stock-based compensation
Vesting (as a percent)			33.00%			33.00%		33.00%	33.00%	25.00%
Certain Senior Management \| Vesting period two \| 2013 Plan \| Time-Based Share Awards \| Nonvested shares
Stock-based compensation
Vesting (as a percent)			33.00%			33.00%		33.00%	33.00%	25.00%
Certain Senior Management \| Vesting period three \| 2013 Plan \| Time-Based Share Awards \| Nonvested shares
Stock-based compensation
Vesting (as a percent)			33.00%			33.00%		33.00%	33.00%	25.00%
Certain Senior Management \| Vesting period four \| 2013 Plan \| Time-Based Share Awards \| Nonvested shares
Stock-based compensation
Vesting (as a percent)										25.00%
Employee \| Time-Based Share Awards \| Nonvested shares
Stock-based compensation
Vesting period							4 years
Employee \| Vesting Based On Performance \| Nonvested shares
Stock-based compensation
Performance period							3 years
Employee \| Vesting period one \| Time-Based Share Awards \| Nonvested shares
Stock-based compensation
Vesting (as a percent)							25.00%
Employee \| Vesting period two \| Time-Based Share Awards \| Nonvested shares
Stock-based compensation
Vesting (as a percent)							25.00%
Employee \| Vesting period three \| Time-Based Share Awards \| Nonvested shares
Stock-based compensation
Vesting (as a percent)							25.00%
Employee \| Vesting period four \| Time-Based Share Awards \| Nonvested shares
Stock-based compensation
Vesting (as a percent)							25.00%
Director \| Time-Based Share Awards \| Nonvested share units \| Maximum
Stock-based compensation
Vesting period		1 year			1 year		1 year
Incentive Program Bonus Award Fiscal Year Performance \| Employee \| Time-Based Share Awards \| Nonvested shares
Stock-based compensation
Vesting period			3 years			3 years		3 years	3 years
Incentive Program Bonus Award Fiscal Year Performance \| Employee \| Time-Based Share Awards \| Nonvested share units
Stock-based compensation
Vesting period			3 years	3 years		3 years		3 years	3 years
Incentive Program Bonus Award Fiscal Year Performance \| Employee \| Vesting period one \| Time-Based Share Awards \| Nonvested shares
Stock-based compensation
Vesting (as a percent)			33.00%			33.00%		33.00%	33.00%
Incentive Program Bonus Award Fiscal Year Performance \| Employee \| Vesting period one \| Time-Based Share Awards \| Nonvested share units
Stock-based compensation
Vesting (as a percent)			33.00%	33.00%		33.00%		33.00%	33.00%
Incentive Program Bonus Award Fiscal Year Performance \| Employee \| Vesting period two \| Time-Based Share Awards \| Nonvested shares
Stock-based compensation
Vesting (as a percent)			33.00%			33.00%		33.00%	33.00%
Incentive Program Bonus Award Fiscal Year Performance \| Employee \| Vesting period two \| Time-Based Share Awards \| Nonvested share units
Stock-based compensation
Vesting (as a percent)			33.00%	33.00%		33.00%		33.00%	33.00%
Incentive Program Bonus Award Fiscal Year Performance \| Employee \| Vesting period three \| Time-Based Share Awards \| Nonvested shares
Stock-based compensation
Vesting (as a percent)			33.00%			33.00%		33.00%	33.00%
Incentive Program Bonus Award Fiscal Year Performance \| Employee \| Vesting period three \| Time-Based Share Awards \| Nonvested share units
Stock-based compensation
Vesting (as a percent)			33.00%	33.00%		33.00%		33.00%	33.00%
Subsequent event \| Certain Senior Management \| Nonvested shares
Stock-based compensation
Granted (in shares)	185,896
Subsequent event \| Certain Employees \| Nonvested share units
Stock-based compensation
Granted (in shares)	90,283

Stock-Based Compensation (Details 2) - Nonvested shares	12 Months Ended
Stock-Based Compensation (Details 2) - Nonvested shares	Dec. 31, 2017
2017 Performance-Based Grants \| Compounded Annual Book Value Per Share Growth 16 %
Stock-based compensation
Compounded Annual Book Value Per Share Growth	16.00%
Nonvested Common Shares Earned	25.00%
2017 Performance-Based Grants \| Compounded Annual Book Value Per Share Growth 17 %
Stock-based compensation
Compounded Annual Book Value Per Share Growth	17.00%
Nonvested Common Shares Earned	50.00%
2017 Performance-Based Grants \| Compounded Annual Book Value Per Share Growth 18 %
Stock-based compensation
Compounded Annual Book Value Per Share Growth	18.00%
Nonvested Common Shares Earned	75.00%
2017 Performance-Based Grants \| Maximum \| Compounded Annual Book Value Per Share Growth 16 %
Stock-based compensation
Compounded Annual Book Value Per Share Growth	16.00%
Nonvested Common Shares Earned	0.00%
2017 Performance-Based Grants \| Minimum \| Compounded Annual Book Value Per Share Growth 19 %
Stock-based compensation
Compounded Annual Book Value Per Share Growth	19.00%
Nonvested Common Shares Earned	100.00%
2016 Performance-Based Grants \| Compounded Annual Book Value Per Share Growth 13%
Stock-based compensation
Compounded Annual Book Value Per Share Growth	13.00%
Nonvested Common Shares Earned	25.00%
2016 Performance-Based Grants \| Compounded Annual Book Value Per Share Growth 14 %
Stock-based compensation
Compounded Annual Book Value Per Share Growth	14.00%
Nonvested Common Shares Earned	50.00%
2016 Performance-Based Grants \| Compounded Annual Book Value Per Share Growth 15%
Stock-based compensation
Compounded Annual Book Value Per Share Growth	15.00%
Nonvested Common Shares Earned	75.00%
2016 Performance-Based Grants \| Maximum \| Compounded Annual Book Value Per Share Growth 13%
Stock-based compensation
Compounded Annual Book Value Per Share Growth	13.00%
Nonvested Common Shares Earned	0.00%
2016 Performance-Based Grants \| Minimum \| Compounded Annual Book Value Per Share Growth 16 %
Stock-based compensation
Compounded Annual Book Value Per Share Growth	16.00%
Nonvested Common Shares Earned	100.00%
2013, 2014 and 2015 Performance-Based Grants \| Compounded Annual Book Value Per Share Growth 16 %
Stock-based compensation
Nonvested Common Shares Earned	100.00%
2013, 2014 and 2015 Performance-Based Grants \| Compounded Annual Book Value Per Share Growth 13%
Stock-based compensation
Compounded Annual Book Value Per Share Growth	13.00%
Nonvested Common Shares Earned	61.00%
2013, 2014 and 2015 Performance-Based Grants \| Compounded Annual Book Value Per Share Growth 14 %
Stock-based compensation
Compounded Annual Book Value Per Share Growth	14.00%
Nonvested Common Shares Earned	87.00%
2013, 2014 and 2015 Performance-Based Grants \| Compounded Annual Book Value Per Share Growth 11%
Stock-based compensation
Compounded Annual Book Value Per Share Growth	11.00%
Nonvested Common Shares Earned	10.00%
2013, 2014 and 2015 Performance-Based Grants \| Compounded Annual Book Value Per Share Growth 12%
Stock-based compensation
Compounded Annual Book Value Per Share Growth	12.00%
Nonvested Common Shares Earned	36.00%
2013, 2014 and 2015 Performance-Based Grants \| Maximum \| Compounded Annual Book Value Per Share Growth 11%
Stock-based compensation
Compounded Annual Book Value Per Share Growth	11.00%
Nonvested Common Shares Earned	0.00%
2013, 2014 and 2015 Performance-Based Grants \| Minimum \| Compounded Annual Book Value Per Share Growth 15%
Stock-based compensation
Compounded Annual Book Value Per Share Growth	15.00%
Nonvested Common Shares Earned	100.00%

Stock-Based Compensation (Details 3) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Nonvested share units
Number of Shares
Outstanding at beginning of year (in shares)	493	544	664
Granted (in shares)	387	215	129
Vested (in shares)	(321)	(254)	(239)
Forfeited (in shares)	(23)	(12)	(10)
Outstanding at end of period (in shares)	536	493	544
Weighted Average Grant Date Fair Value
Outstanding at beginning of year (in dollars per share)	$ 19.24	$ 19.84	$ 18.32
Granted (in dollars per share)	33.40	18.21	24.47
Vested (in dollars per share)	19.00	19.71	18.18
Forfeited (in dollars per share)	30.49	18.12	17.89
Outstanding at end of period (in dollars per share)	$ 29.13	$ 19.24	$ 19.84
Time and Performance- Based Share Awards \| Nonvested shares
Number of Shares
Outstanding at beginning of year (in shares)	1,503	1,294	1,290
Granted (in shares)	140	209	50
Vested (in shares)	(48)	0	0
Forfeited (in shares)	0	0	(46)
Outstanding at end of period (in shares)	1,595	1,503	1,294
Weighted Average Grant Date Fair Value
Outstanding at beginning of year (in dollars per share)	$ 15.41	$ 15.15	$ 14.83
Granted (in dollars per share)	36.29	17.01	24.58
Vested (in dollars per share)	22.48
Forfeited (in dollars per share)			16.40
Outstanding at end of period (in dollars per share)	$ 17.03	$ 15.41	$ 15.15
Time-Based Share Awards \| Nonvested shares
Number of Shares
Outstanding at beginning of year (in shares)	605	890	1,472
Granted (in shares)	91	181	109
Vested (in shares)	(286)	(461)	(644)
Forfeited (in shares)	0	(5)	(47)
Outstanding at end of period (in shares)	410	605	890
Weighted Average Grant Date Fair Value
Outstanding at beginning of year (in dollars per share)	$ 16.32	$ 12.31	$ 9.04
Granted (in dollars per share)	36.29	17.01	24.51
Vested (in dollars per share)	15.74	9.04	6.67
Forfeited (in dollars per share)		0.23	15.50
Outstanding at end of period (in dollars per share)	$ 21.12	$ 16.32	$ 12.31

Stock-Based Compensation (Details 4) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Compensation expense	$ 18,688	$ 16,881	$ 13,633
Income tax benefit	$ 6,017	$ 5,455	$ 4,378

Dividends Restrictions (Details) - USD ($)	12 Months Ended
Dividends Restrictions (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Dividends Restrictions
Dividends paid to parent company	$ 0	$ 0	$ 0
Essent Guaranty And Essent PA
Dividends Restrictions
Dividend payment ability, period of payment of dividends (in months)	12 months
Dividend payment ability, as a percentage of preceding year-end statutory policyholders' surplus	10.00%
Essent Guaranty
Dividends Restrictions
Unassigned surplus	$ 70,700,000
Dividends paid to parent company	$ 0	0	0
Essent PA
Dividends Restrictions
Dividend payment ability, period of payment of dividends (in months)	12 months
Dividend payment ability, as a percentage of preceding year-end statutory policyholders' surplus	10.00%
Unassigned surplus	$ 6,500,000
Dividends paid to parent company	$ 5,000,000	$ 3,750,000	$ 0

Dividends Restrictions (Details 2) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Equity
Total equity	$ 1,940,436,000	$ 1,343,773,000	$ 1,119,241,000	$ 955,738,000
Essent Re
Equity
Total equity	662,800,000
Essent Re \| Minimum \| Essent Guaranty \| Quota share reinsurance
Equity
Total equity	$ 100,000,000

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Statutory rate (as a percent)									35.00%
Income before income taxes	$ 105,357	$ 107,399	$ 98,961	$ 86,851	$ 87,302	$ 83,441	$ 73,792	$ 67,347	$ 398,568	$ 311,882	$ 228,398
Tax Cuts and Jobs Act of 2017 tax expense (benefit)									(85,091)	0	0
Components of income tax expense
Current									38,252	31,712	18,910
Deferred									65,660	57,564	52,157
Remeasurement of net deferred tax liability for enacted changes in tax law									(85,091)	0	0
Total income tax expense									18,821	89,276	71,067
Effective Income Tax Rate Reconciliation, Amount
Tax provision at weighted average statutory rates									109,309	91,092	72,461
Change in valuation of net deferred tax liability									(85,091)	0	0
Excess tax benefits from stock-based compensation									(3,227)	0	0
Tax exempt interest, net of proration									(2,608)	(2,181)	(1,741)
Non-deductible expenses									392	378	381
Other									46	(13)	(34)
Total income tax expense									$ 18,821	$ 89,276	$ 71,067
% of pretax income
Tax provision (benefit) at weighted average statutory rates (as a percent)									27.40%	29.20%	31.70%
Change in valuation of net deferred tax liability (as a percent)									(21.30%)	0.00%	0.00%
Excess tax benefits from stock-based compensation (as a percent)									(0.80%)	(0.00%)	(0.00%)
Tax exempt interest, net of proration (as a percent)									(0.70%)	(0.70%)	(0.80%)
Non-deductible expenses (as a percent)									0.10%	0.10%	0.20%
Other (as a percent)									0.00%	0.00%	0.00%
Total income tax expense (as a percent)									4.70%	28.60%	31.10%
Bermuda \| Bermuda
Operating Loss Carryforwards [Line Items]
Statutory rate (as a percent)									0.00%
Office of the Tax Commissioner, Bermuda \| Bermuda
Operating Loss Carryforwards [Line Items]
Income before income taxes									$ 86,300	$ 51,600	$ 21,400
Internal Revenue Service (IRS) \| U.S.
Operating Loss Carryforwards [Line Items]
Income before income taxes									$ 312,300	$ 260,300	$ 207,000

Income Taxes (Details 2) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Net deferred tax asset
Deferred tax assets	$ 28,696	$ 43,291
Deferred tax liabilities	(156,332)	(185,878)
Net deferred tax liability	(127,636)	(142,587)
Components of the net deferred tax asset
Contingency reserves	(151,586)	(181,031)
Unearned premium reserve	14,454	19,722
Nonvested shares	6,442	8,445
Deferred policy acquisition costs	(3,224)	(4,690)
Unearned ceding commissions	2,815	3,568
Fixed assets	2,529	4,702
Start-up expenditures, net	1,951	3,705
Unrealized (gain) loss on investments	1,403
Unrealized (gain) loss on investments		(2,181)
Accrued expenses	335	775
Loss reserves	158	170
Prepaid expenses	(119)	(157)
Organizational expenditures	12	23
Net deferred tax liability	$ (127,636)	$ (142,587)

Income Taxes (Details 3) - USD ($) $ in Thousands	12 Months Ended
Income Taxes (Details 3) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Net purchases of T&L Bonds	$ 70,885	$ 61,860	$ 59,739
T&L Bonds held as of end of year	$ 252,157	$ 181,272

Income Taxes (Details 4) - USD ($)	12 Months Ended
Income Taxes (Details 4) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits	$ 0	$ 0
Liability for uncertain tax positions	0	$ 0
U.S.
Operating Loss Carryforwards [Line Items]
Taxes provided on un-remitted earnings	0
Cumulative amount of earnings that would be subject to withholding tax, if distributed outside of the U.S.	846,800,000
Essent Irish Intermediate \| Essent Holdings
Operating Loss Carryforwards [Line Items]
Withholding taxes accrued with respect to un-remitted earnings	0
United States Ireland Tax Treaty Benefits Availed \| U.S.
Operating Loss Carryforwards [Line Items]
Associated withholding tax liability on cumulative amount of earnings that would be subject to withholding tax, if distributed outside of the U.S.	$ 42,300,000
United States Ireland Tax Treaty Benefits Availed \| Essent Irish Intermediate \| Essent Holdings
Operating Loss Carryforwards [Line Items]
Withholding tax rate on dividends paid (as a percent)	5.00%
Absent Benefits Of United States Ireland Tax Treaty \| Essent Irish Intermediate \| Essent Holdings
Operating Loss Carryforwards [Line Items]
Withholding tax rate on dividends paid (as a percent)	30.00%

Related Party Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Nov. 05, 2013
Related Party Transactions
Debt issuance costs, gross	$ 0		$ 1,409
Goldman Sachs \| Essent Group \| Investor
Related Party Transactions
Percentage of outstanding shares held by investor (less than after IPO)				11.35%
Goldman Sachs \| Essent Group \| Maximum \| Investor
Related Party Transactions
Percentage of outstanding shares held by investor (less than after IPO)				10.00%
Goldman Sachs Asset Management L.P. \| Investor \| Investment advisory agreement
Related Party Transactions
Expense incurred	800	$ 700
Goldman Sachs Asset Management L.P. \| Investor \| Revolving Credit Facility
Related Party Transactions
Debt issuance costs, gross	100
Commitment fees and interest incurred	$ 100

Earnings per Share (EPS) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net income	$ 162,638	$ 78,393	$ 72,118	$ 66,598	$ 62,686	$ 59,711	$ 52,258	$ 47,951	$ 379,747	$ 222,606	$ 157,331
Less: Common Shares dividends declared									0	0	0
Undistributed net income									379,747	222,606	157,331
Net income allocable to Common									$ 379,747	$ 222,606	$ 157,331
Basic earnings per share (in dollars per share)	$ 1.69	$ 0.83	$ 0.79	$ 0.73	$ 0.69	$ 0.66	$ 0.57	$ 0.53	$ 4.07	$ 2.45	$ 1.74
Diluted earnings per share (in dollars per share)	$ 1.65	$ 0.82	$ 0.77	$ 0.72	$ 0.68	$ 0.65	$ 0.57	$ 0.52	$ 3.99	$ 2.41	$ 1.72
Basic weighted average Common Shares outstanding (in shares)	96,429	94,185	91,381	91,258	90,991	90,961	90,912	90,785	93,330	90,913	90,351
Dilutive effect of nonvested shares (in shares)									1,881	1,332	1,387
Diluted weighted average Common Shares outstanding (in shares)	98,497	96,094	93,162	93,023	92,577	92,399	92,138	91,859	95,211	92,245	91,738

Earnings per Share (EPS) (Details 2) - shares	12 Months Ended
Earnings per Share (EPS) (Details 2) - shares	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Contingently issuable awards
Antidilutive nonvested shares	44,540	96,251	78,198
Performance-based share awards
Contingently issuable awards
Percentage of award issuable if current period end were end of contingency period	100.00%	100.00%	100.00%

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other comprehensive income (loss):
Other comprehensive income (loss), before tax	$ 12,587	$ (15,097)
Other comprehensive income (loss):
Other comprehensive income (loss), tax effect	(4,519)	2,941
Net of Tax
Stockholders equity, beginning of period	1,343,773	1,119,241	$ 955,738
Other comprehensive income (loss):
Total other comprehensive income (loss)	8,068	(12,156)	(4,766)
Stockholders equity, end of period	1,940,436	1,343,773	1,119,241
Accumulated Other Comprehensive Income (Loss)
Before Tax
AOCI before tax, beginning of period	(14,436)	661
Other comprehensive income (loss):
AOCI before tax, end of period	(1,849)	(14,436)	661
Tax Effect
AOCI tax effect, beginning of period	2,181	(760)
Other comprehensive income (loss):
AOCI tax effect, end of period	(1,403)	2,181	(760)
Net of Tax
Stockholders equity, beginning of period	(12,255)	(99)	4,667
Other comprehensive income (loss):
Total other comprehensive income (loss)	8,068	(12,156)	(4,766)
Reclassification of certain income tax effects resulting from tax reform	935
Stockholders equity, end of period	(3,252)	(12,255)	$ (99)
Accumulated Net Investment Gain (Loss) Attributable to Parent
Other comprehensive income (loss):
Unrealized holding gains (losses) arising during the period, before tax	14,602	(13,156)
Less: Reclassification adjustment for gains included in net income, before tax	(2,015)	(1,941)
Other comprehensive income (loss), before tax	12,587	(15,097)
Other comprehensive income (loss):
Unrealized holding (gains) losses arising during the period, tax effect	(5,239)	2,376
Less: Reclassification adjustment for gains included in net income, tax effect	720	565
Other comprehensive income (loss), tax effect	(4,519)	2,941
Other comprehensive income (loss):
Unrealized holding gains (losses) arising during the period, net of tax	9,363	(10,780)
Less: Reclassification adjustment for gains included in net income, net of tax	(1,295)	(1,376)
Total other comprehensive income (loss)	$ 8,068	$ (12,156)

Fair Value of Financial Instruments (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Recurring fair value measurements
Fair Value	$ 2,305,065,000	$ 1,615,102,000
U.S. Treasury securities
Recurring fair value measurements
Fair Value	227,805,000	191,548,000
Municipal debt securities
Recurring fair value measurements
Fair Value	465,255,000	334,324,000
Corporate debt securities
Recurring fair value measurements
Fair Value	611,728,000	456,357,000
Residential and commercial mortgage securities
Recurring fair value measurements
Fair Value	79,407,000	68,336,000
Asset-backed securities
Recurring fair value measurements
Fair Value	167,922,000	127,172,000
Money market funds
Recurring fair value measurements
Fair Value	263,797,000	102,430,000
U.S. Agency \| U.S. agency securities
Recurring fair value measurements
Fair Value	33,114,000	18,441,000
U.S. Agency \| U.S. agency mortgage-backed securities
Recurring fair value measurements
Fair Value	456,037,000	316,494,000
Recurring basis
Recurring fair value measurements
Total assets at fair value	2,305,065,000	1,615,102,000
Recurring basis \| U.S. Treasury securities
Recurring fair value measurements
Fair Value	227,805,000	191,548,000
Recurring basis \| Municipal debt securities
Recurring fair value measurements
Fair Value	465,255,000	334,324,000
Recurring basis \| Corporate debt securities
Recurring fair value measurements
Fair Value	611,728,000	456,357,000
Recurring basis \| Residential and commercial mortgage securities
Recurring fair value measurements
Fair Value	79,407,000	68,336,000
Recurring basis \| Asset-backed securities
Recurring fair value measurements
Fair Value	167,922,000	127,172,000
Recurring basis \| Money market funds
Recurring fair value measurements
Fair Value	263,797,000	102,430,000
Recurring basis \| U.S. Agency \| U.S. agency securities
Recurring fair value measurements
Fair Value	33,114,000	18,441,000
Recurring basis \| U.S. Agency \| U.S. agency mortgage-backed securities
Recurring fair value measurements
Fair Value	456,037,000	316,494,000
Recurring basis \| Quoted Prices in Active Markets for Identical Instruments (Level 1)
Recurring fair value measurements
Total assets at fair value	491,602,000	293,978,000
Recurring basis \| Quoted Prices in Active Markets for Identical Instruments (Level 1) \| U.S. Treasury securities
Recurring fair value measurements
Fair Value	227,805,000	191,548,000
Recurring basis \| Quoted Prices in Active Markets for Identical Instruments (Level 1) \| Municipal debt securities
Recurring fair value measurements
Fair Value	0	0
Recurring basis \| Quoted Prices in Active Markets for Identical Instruments (Level 1) \| Corporate debt securities
Recurring fair value measurements
Fair Value	0	0
Recurring basis \| Quoted Prices in Active Markets for Identical Instruments (Level 1) \| Residential and commercial mortgage securities
Recurring fair value measurements
Fair Value	0	0
Recurring basis \| Quoted Prices in Active Markets for Identical Instruments (Level 1) \| Asset-backed securities
Recurring fair value measurements
Fair Value	0	0
Recurring basis \| Quoted Prices in Active Markets for Identical Instruments (Level 1) \| Money market funds
Recurring fair value measurements
Fair Value	263,797,000	102,430,000
Recurring basis \| Quoted Prices in Active Markets for Identical Instruments (Level 1) \| U.S. Agency \| U.S. agency securities
Recurring fair value measurements
Fair Value	0	0
Recurring basis \| Quoted Prices in Active Markets for Identical Instruments (Level 1) \| U.S. Agency \| U.S. agency mortgage-backed securities
Recurring fair value measurements
Fair Value	0	0
Recurring basis \| Significant Other Observable Inputs (Level 2)
Recurring fair value measurements
Total assets at fair value	1,813,463,000	1,321,124,000
Recurring basis \| Significant Other Observable Inputs (Level 2) \| U.S. Treasury securities
Recurring fair value measurements
Fair Value	0	0
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Municipal debt securities
Recurring fair value measurements
Fair Value	465,255,000	334,324,000
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Corporate debt securities
Recurring fair value measurements
Fair Value	611,728,000	456,357,000
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Residential and commercial mortgage securities
Recurring fair value measurements
Fair Value	79,407,000	68,336,000
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Asset-backed securities
Recurring fair value measurements
Fair Value	167,922,000	127,172,000
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Money market funds
Recurring fair value measurements
Fair Value	0	0
Recurring basis \| Significant Other Observable Inputs (Level 2) \| U.S. Agency \| U.S. agency securities
Recurring fair value measurements
Fair Value	33,114,000	18,441,000
Recurring basis \| Significant Other Observable Inputs (Level 2) \| U.S. Agency \| U.S. agency mortgage-backed securities
Recurring fair value measurements
Fair Value	456,037,000	316,494,000
Recurring basis \| Significant Unobservable Inputs (Level 3)
Recurring fair value measurements
Total assets at fair value	0	0
Recurring basis \| Significant Unobservable Inputs (Level 3) \| U.S. Treasury securities
Recurring fair value measurements
Fair Value	0	0
Recurring basis \| Significant Unobservable Inputs (Level 3) \| Municipal debt securities
Recurring fair value measurements
Fair Value	0	0
Recurring basis \| Significant Unobservable Inputs (Level 3) \| Corporate debt securities
Recurring fair value measurements
Fair Value	0	0
Recurring basis \| Significant Unobservable Inputs (Level 3) \| Residential and commercial mortgage securities
Recurring fair value measurements
Fair Value	0	0
Recurring basis \| Significant Unobservable Inputs (Level 3) \| Asset-backed securities
Recurring fair value measurements
Fair Value	0	0
Recurring basis \| Significant Unobservable Inputs (Level 3) \| Money market funds
Recurring fair value measurements
Fair Value	0	0
Recurring basis \| Significant Unobservable Inputs (Level 3) \| U.S. Agency \| U.S. agency securities
Recurring fair value measurements
Fair Value	0	0
Recurring basis \| Significant Unobservable Inputs (Level 3) \| U.S. Agency \| U.S. agency mortgage-backed securities
Recurring fair value measurements
Fair Value	$ 0	$ 0

Fair Value of Financial Instruments (Details 2) - Recurring basis - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	$ 2,305,065,000	$ 1,615,102,000
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	$ 0	$ 0

Fair Value of Financial Instruments (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Level 3 Liabilities
Fair value of derivative liabilities at beginning of period	$ 0	$ 1,232
Net realized and unrealized losses (gains) included in income	0	(1,934)
Other comprehensive (income) loss	0	0
Purchases, sales, issues and settlements, net	0	702
Gross transfers in	0	0
Gross transfers out	0	0
Fair value of derivative liabilities at end of period	0	0
Changes in net unrealized losses (gains) included in income on instruments held at end of period	$ 0	$ (1,934)

Statutory Accounting (Details) - USD ($) $ in Thousands	12 Months Ended
Statutory Accounting (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Essent Guaranty
Dividends Restrictions
Statutory net income	$ 261,811	$ 215,951	$ 172,688
Statutory surplus	761,006	578,887	522,172
Contingency reserve liability	678,701	480,829	315,058
Increase in contingency reserve	197,900
Essent PA
Dividends Restrictions
Statutory net income	10,250	12,978	15,200
Statutory surplus	45,509	47,387	47,139
Contingency reserve liability	43,141	36,401	$ 27,502
Increase in contingency reserve	6,700
Essent Re
Dividends Restrictions
Statutory net income	96,900	$ 56,700
Statutory capital and surplus	$ 662,600

Capital Maintenance Agreement (Details)	Dec. 31, 2017 USD ($)
Essent Guaranty \| Capital maintenance agreement \| Essent PA
Capital Maintenance Agreement
Amounts outstanding	$ 0
Essent Guaranty \| Capital maintenance agreement \| Essent PA \| Maximum
Capital Maintenance Agreement
Risk to capital ratio	25.0
Essent PA
Capital Maintenance Agreement
Risk to capital ratio	5.4

Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Net premiums earned	$ 147,976	$ 137,940	$ 126,563	$ 117,651	$ 116,792	$ 110,801	$ 100,711	$ 94,403	$ 530,130	$ 422,707	$ 326,471
Other revenues	13,134	12,263	11,043	9,941	9,581	10,453	7,454	8,063
Provision for losses and LAE	17,456	4,313	1,770	3,693	3,865	4,965	2,964	3,731
Other underwriting and operating expenses	36,480	37,035	35,686	36,332	34,836	32,792	31,409	31,388	145,533	130,425	112,987
Interest expense	1,817	1,456	1,189	716	370	56	0	0	5,178	426	0
Income before income taxes	105,357	107,399	98,961	86,851	87,302	83,441	73,792	67,347	398,568	311,882	228,398
Net income	$ 162,638	$ 78,393	$ 72,118	$ 66,598	$ 62,686	$ 59,711	$ 52,258	$ 47,951	$ 379,747	$ 222,606	$ 157,331
Basic earnings per Common Share (in dollars per share)	$ 1.69	$ 0.83	$ 0.79	$ 0.73	$ 0.69	$ 0.66	$ 0.57	$ 0.53	$ 4.07	$ 2.45	$ 1.74
Diluted earnings per Common Share (in dollars per share)	$ 1.65	$ 0.82	$ 0.77	$ 0.72	$ 0.68	$ 0.65	$ 0.57	$ 0.52	$ 3.99	$ 2.41	$ 1.72
Basic weighted average Common Shares outstanding (in shares)	96,429	94,185	91,381	91,258	90,991	90,961	90,912	90,785	93,330	90,913	90,351
Diluted weighted average Common Shares outstanding (in shares)	98,497	96,094	93,162	93,023	92,577	92,399	92,138	91,859	95,211	92,245	91,738

Schedule I-Summary of Investments-Other Than Investments in Related Parties (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Investments-Other Than Investments in Related Parties
Amortized Cost	$ 2,306,914	$ 1,629,538
Fair Value	2,305,065	1,615,102
Amount at which shown in the Balance Sheet	2,305,065
Residential and commercial mortgage securities
Investments-Other Than Investments in Related Parties
Amortized Cost	78,974	68,430
Fair Value	79,407	68,336
Asset-backed securities
Investments-Other Than Investments in Related Parties
Amortized Cost	167,638	127,359
Fair Value	167,922	127,172
Fixed maturities
Investments-Other Than Investments in Related Parties
Amortized Cost	1,994,200	1,497,186
Fair Value	1,992,371
Amount at which shown in the Balance Sheet	1,992,371
Fixed maturities \| United States Government and government agencies and authorities
Investments-Other Than Investments in Related Parties
Amortized Cost	679,654
Fair Value	668,059
Amount at which shown in the Balance Sheet	668,059
Fixed maturities \| States, municipalities and political subdivisions
Investments-Other Than Investments in Related Parties
Amortized Cost	457,418
Fair Value	465,255
Amount at which shown in the Balance Sheet	465,255
Fixed maturities \| Residential and commercial mortgage securities
Investments-Other Than Investments in Related Parties
Amortized Cost	78,974
Fair Value	79,407
Amount at which shown in the Balance Sheet	79,407
Fixed maturities \| Asset-backed securities
Investments-Other Than Investments in Related Parties
Amortized Cost	167,638
Fair Value	167,922
Amount at which shown in the Balance Sheet	167,922
Fixed maturities \| All other corporate bonds
Investments-Other Than Investments in Related Parties
Amortized Cost	610,516
Fair Value	611,728
Amount at which shown in the Balance Sheet	611,728
Short-term investments
Investments-Other Than Investments in Related Parties
Amortized Cost	312,714	$ 132,352
Fair Value	312,694
Amount at which shown in the Balance Sheet	$ 312,694

Schedule II-Condensed Financial Information of Registrant (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Investments
Fixed maturities (amortized cost: 2017 — $0; 2016 — $10,002)	$ 1,992,371	$ 1,482,754
Short-term investments (amortized cost: 2017 — $97,926; 2016 — $32,039)	312,694	132,348
Total investments	2,305,065	1,615,102
Cash	43,524	27,531
Other assets	8,730	6,454
Total assets	2,674,368	1,882,998
Liabilities
Credit facility borrowings (at carrying value, less unamortized deferred costs of $1,409 in 2017 and $0 in 2016)	248,591	100,000
Other accrued liabilities	36,184	33,881
Total liabilities	733,932	539,225
Commitments and contingencies
Stockholders' Equity
Common shares	1,476	1,397
Additional paid-in capital	1,127,137	918,296
Accumulated other comprehensive loss	(3,252)	(12,255)
Retained earnings	815,075	436,335
Total stockholders' equity	1,940,436	1,343,773	$ 1,119,241	$ 955,738
Total liabilities and stockholders' equity	2,674,368	1,882,998
Parent Company
Investments
Fixed maturities (amortized cost: 2017 — $0; 2016 — $10,002)	0	10,004
Short-term investments (amortized cost: 2017 — $97,926; 2016 — $32,039)	97,917	32,036
Total investments	97,917	42,040
Cash	6,250	4,521
Due from affiliates	987	1,750
Investment in consolidated subsidiaries	1,956,955	1,393,720
Other assets	2,662	2,452
Total assets	2,064,771	1,444,483
Liabilities
Credit facility borrowings (at carrying value, less unamortized deferred costs of $1,409 in 2017 and $0 in 2016)	123,591	100,000
Other accrued liabilities	744	710
Total liabilities	124,335	100,710
Commitments and contingencies
Stockholders' Equity
Common shares	1,476	1,397
Additional paid-in capital	1,127,137	918,296
Accumulated other comprehensive loss	(3,252)	(12,255)
Retained earnings	815,075	436,335
Total stockholders' equity	1,940,436	1,343,773
Total liabilities and stockholders' equity	$ 2,064,771	$ 1,444,483

Schedule II-Condensed Financial Information of Registrant (Parenthetical) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Balance Sheets
Amortized cost	$ 2,306,914	$ 1,629,538
Unamortized deferred costs	1,409	0
Parent Company
Balance Sheets
Unamortized deferred costs	1,409	0
Short-term investments
Balance Sheets
Amortized cost	312,714	132,352
Short-term investments \| Parent Company
Balance Sheets
Amortized cost	97,926	32,039
Fixed maturities
Balance Sheets
Amortized cost	1,994,200	1,497,186
Fixed maturities \| Parent Company
Balance Sheets
Amortized cost	$ 0	$ 10,002

Schedule II-Condensed Financial Information of Registrant (Details 2) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Net investment income									$ 40,226	$ 27,890	$ 19,885
Total revenues									576,511	458,258	353,290
Expenses:
Interest expense	$ 1,817	$ 1,456	$ 1,189	$ 716	$ 370	$ 56	$ 0	$ 0	5,178	426	0
Income before income taxes	105,357	107,399	98,961	86,851	87,302	83,441	73,792	67,347	398,568	311,882	228,398
Net income	$ 162,638	$ 78,393	$ 72,118	$ 66,598	$ 62,686	$ 59,711	$ 52,258	$ 47,951	379,747	222,606	157,331
Other comprehensive income (loss):
Change in unrealized appreciation (depreciation) of investments, net of tax expense (benefit) of $4,519 in 2017, ($2,941) in 2016 and ($1,285) in 2015									8,068	(12,156)	(4,766)
Change in unrealized appreciation (depreciation) of investments, tax expense (benefit)									4,519	(2,941)	(1,285)
Total other comprehensive income (loss)									8,068	(12,156)	(4,766)
Comprehensive income									387,815	210,450	152,565
Parent Company
Revenues:
Net investment income									494	284	421
Realized investment (losses) gains, net									(2)	111	(181)
Administrative service fees from subsidiaries									489	473	437
Total revenues									981	868	677
Expenses:
Administrative service fees to subsidiaries									2,127	1,760	1,762
Other operating expenses									4,968	4,832	3,554
Interest expense									4,371	426	0
Total expenses									11,466	7,018	5,316
Income before income taxes									(10,485)	(6,150)	(4,639)
Loss before equity in undistributed net income of subsidiaries									(10,485)	(6,150)	(4,639)
Equity in undistributed net income of subsidiaries									390,232	228,756	161,970
Net income									379,747	222,606	157,331
Other comprehensive income (loss):
Change in unrealized appreciation (depreciation) of investments, net of tax expense (benefit) of $4,519 in 2017, ($2,941) in 2016 and ($1,285) in 2015									8,068	(12,156)	(4,766)
Change in unrealized appreciation (depreciation) of investments, tax expense (benefit)									4,519	(2,941)	(1,285)
Total other comprehensive income (loss)									8,068	(12,156)	(4,766)
Comprehensive income									$ 387,815	$ 210,450	$ 152,565

Schedule II-Condensed Financial Information of Registrant (Details 3) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	Aug. 31, 2017	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities
Net income		$ 162,638	$ 78,393	$ 72,118	$ 66,598	$ 62,686	$ 59,711	$ 52,258	$ 47,951	$ 379,747	$ 222,606	$ 157,331
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense										18,688	16,881	13,633
Amortization of premium on investment securities										12,038	10,486	10,004
Changes in assets and liabilities:
Other assets										(1,408)	(526)	(724)
Net cash provided by operating activities										368,573	274,559	226,559
Investing Activities
Net change in short-term investments										(180,346)	(46,352)	124,692
Purchase of investments available for sale										(833,298)	(656,768)	(798,891)
Proceeds from maturity of investments available for sale										71,908	27,186	8,613
Proceeds from sales of investments available for sale										254,377	313,780	449,834
Net cash used in investing activities										(690,142)	(365,316)	(220,712)
Financing Activities
Issuance of common shares, net of costs	$ 197,700									197,829	0	(537)
Credit facility borrowings										200,000	100,000	0
Credit facility repayments										(50,000)	0	0
Treasury stock acquired										(7,577)	(4,024)	(5,168)
Payment of issuance costs for credit facility										(2,690)	(2,436)	0
Other financing activities										0	142	53
Net cash provided by (used in) financing activities										337,562	93,682	(5,652)
Net increase in cash										15,993	2,925	195
Cash at beginning of year					27,531				24,606	27,531	24,606	24,411
Cash at end of year		43,524				27,531				43,524	27,531	24,606
Supplemental Disclosure of Cash Flow Information
Interest payments										(4,685)	(324)	0
Parent Company
Operating Activities
Net income										379,747	222,606	157,331
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in net income of subsidiaries										(390,232)	(228,756)	(161,970)
Loss (gain) on the sale of investments, net										2	(111)	181
Stock-based compensation expense										807	880	880
Amortization of premium on investment securities										0	169	399
Changes in assets and liabilities:
Other assets										1,421	121	(40)
Other accrued liabilities										18,236	17,433	15,153
Net cash provided by operating activities										9,981	12,342	11,934
Investing Activities
Net change in short-term investments										(65,887)	(6,525)	91,119
Investments in subsidiaries										(164,927)	(130,101)	(61,328)
Purchase of investments available for sale										0	0	(130,461)
Proceeds from maturity of investments available for sale										10,000	10,000	0
Proceeds from sales of investments available for sale										0	16,582	94,429
Net cash used in investing activities										(220,814)	(110,044)	(6,241)
Financing Activities
Issuance of common shares, net of costs										197,829	0	(537)
Credit facility borrowings										75,000	100,000	0
Credit facility repayments										(50,000)	0	0
Treasury stock acquired										(7,577)	(4,024)	(5,168)
Payment of issuance costs for credit facility										(2,690)	(2,436)	0
Other financing activities										0	142	53
Net cash provided by (used in) financing activities										212,562	93,682	(5,652)
Net increase in cash										1,729	(4,020)	41
Cash at beginning of year					$ 4,521				$ 8,541	4,521	8,541	8,500
Cash at end of year		$ 6,250				$ 4,521				6,250	4,521	8,541
Supplemental Disclosure of Cash Flow Information
Interest payments										(4,045)	(324)	0
Noncash Transactions
Repayment of borrowings with term loan proceeds (see Note C)										$ (125,000)	$ 0	$ 0

Schedule II-Condensed Financial Information of Registrant (Details 4) - USD ($)			12 Months Ended
	May 17, 2017	Apr. 19, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Information of Registrant
Dividends paid to parent company			$ 0	$ 0	$ 0
Credit facility, maximum borrowing capacity	$ 375,000,000
Essent PA
Condensed Financial Information of Registrant
Dividend payment ability, period of payment of dividends (in months)			12 months
Dividend payment ability, as a percentage of preceding year-end statutory policyholders' surplus			10.00%
Unassigned surplus			$ 6,500,000
Dividends paid to parent company			5,000,000	3,750,000	0
Essent Guaranty
Condensed Financial Information of Registrant
Unassigned surplus			70,700,000
Dividends paid to parent company			$ 0	$ 0	$ 0
Revolving Credit Facility
Condensed Financial Information of Registrant
Credit facility, term	4 years	3 years
Credit facility, maximum borrowing capacity	$ 250,000,000	$ 200,000,000
Term Loan
Condensed Financial Information of Registrant
Credit facility, maximum borrowing capacity	125,000,000
Uncommitted Line
Condensed Financial Information of Registrant
Credit facility, maximum borrowing capacity	$ 75,000,000