NMI (NMIH) 10-K 14 Feb 20 2019 FY Annual report Financial data

Cover Page

Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 11, 2020	Jun. 30, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	001-36174
Entity Registrant Name	NMI Holdings, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	45-4914248
Entity Address, Address Line One	2100 Powell Street
Entity Address, City or Town	Emeryville
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94608
City Area Code	855
Local Phone Number	530-6642
Title of 12(b) Security	Class A Common Stock, $.01 par value per share
Trading Symbol	NMIH
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 1,617,138,263
Entity Common Stock, Shares Outstanding		68,438,109
Documents Incorporated by Reference	the registrant's Proxy Statement for the 2020 Annual Meeting of Stockholders are incorporated herein by reference in Part III of this Annual Report on Form 10-K to the extent stated herein. Such Proxy Statement will be filed with the Securities and Exchange Commission within 120 days of the registrant's fiscal year ended December 31, 2019.
Entity Central Index Key	0001547903
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands		Dec. 31, 2019	Dec. 31, 2018
Assets
Fixed maturities, available-for-sale, at fair value (amortized cost of $1,113,779 and $924,987 as of December 31, 2019 and December 31, 2018, respectively)		$ 1,140,940	$ 911,490
Cash and cash equivalents (including restricted cash of $2,662 and $1,414 as of December 31, 2019 and December 31, 2018, respectively)		41,089	25,294
Premiums receivable		46,085	36,007
Accrued investment income		6,831	5,694
Prepaid expenses		3,512	3,241
Deferred policy acquisition costs, net		59,972	46,840
Software and equipment, net		26,096	24,765
Intangible assets and goodwill		3,634	3,634
Prepaid reinsurance premiums		15,488	30,370
Other assets		21,171	4,708
Total assets		1,364,818	1,092,043
Liabilities
Term loan		145,764	146,757
Unearned premiums		136,642	158,893
Accounts payable and accrued expenses		39,904	31,141
Reserve for insurance claims and claim expenses		23,752	12,811
Reinsurance funds withheld		14,310	27,114
Warrant liability, at fair value		7,641	7,296
Deferred tax liability, net		56,360	2,740
Other liabilities	[1]	10,025	3,791
Total liabilities		434,398	390,543
Commitments and contingencies (see Note 14)
Shareholders' equity
Common stock - class A shares, $0.01 par value; 68,358,074 and 66,318,849 shares issued and outstanding as of December 31, 2019 and December 31, 2018, respectively (250,000,000 shares authorized)		684	663
Additional paid-in capital		707,003	682,181
Accumulated other comprehensive income (loss), net of tax		17,288	(14,832)
Retained earnings		205,445	33,488
Total shareholders' equity		930,420	701,500
Total liabilities and shareholders' equity		$ 1,364,818	$ 1,092,043
[1]	"Deferred Ceding Commissions" have been reclassified as "Other liabilities" in prior periods.

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Fixed maturities, available-for-sale, amortized cost	$ 1,113,779	$ 924,987
Restricted cash	$ 2,662	$ 1,414
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Common stock, issued (in shares)	68,358,074	66,318,849
Common stock, outstanding (in shares)	68,358,074	66,318,849
Common stock, authorized (in shares)	250,000,000	250,000,000

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Revenues
Net premiums earned	$ 95,517	$ 92,381	$ 83,249	$ 73,868	$ 69,261	$ 65,407	$ 61,615	$ 54,914	$ 345,015		$ 251,197		$ 165,740
Net investment income	7,962	7,882	7,629	7,383	6,952	6,277	5,735	4,574	30,856		23,538		16,273
Net realized investment gains	264	81	(113)	(187)	6	(8)	59	0	45		57		208
Other revenues	1,154	1,244	415	42	40	85	44	64	2,855		233		522
Total revenues									378,771		275,025		182,743
Expenses
Insurance claims and claim expenses	4,269	2,572	2,923	2,743	2,141	1,099	643	1,569	12,507		5,452		5,339
Underwriting and operating expenses	31,296	32,335	32,190	30,800	29,339	30,323	28,958	28,346	126,621	[1]	116,966	[1]	106,362	[1]
Service expenses	937	909	353	49	45	56	62	107	2,248	[1]	270	[1]	617	[1]
Interest expense	2,974	2,979	3,071	3,061	3,028	2,972	5,560	3,419	12,085		14,979		13,528
Loss from change in fair value of warrant liability	2,632	(1,139)	1,685	5,479	(3,538)	5,464	(109)	(420)	8,657		1,397		4,105
Total expenses									162,118		139,064		129,951
Income before income taxes	62,789	63,932	50,958	38,974	45,244	31,847	32,339	26,531	216,653		135,961		52,792
Income tax expense	12,594	14,169	11,858	6,075	9,724	7,036	7,098	4,176	44,696		28,034		30,742
Net income	$ 50,195	$ 49,763	$ 39,100	$ 32,899	$ 35,520	$ 24,811	$ 25,241	$ 22,355	$ 171,957		$ 107,927		$ 22,050
Earnings per share
Basic (in dollars per share)	$ 0.74	$ 0.73	$ 0.58	$ 0.49	$ 0.54	$ 0.38	$ 0.38	$ 0.36	$ 2.54		$ 1.66		$ 0.37
Diluted (in dollars per share)	$ 0.71	$ 0.69	$ 0.56	$ 0.48	$ 0.46	$ 0.36	$ 0.37	$ 0.34	$ 2.47		$ 1.60		$ 0.35
Weighted average common shares outstanding
Basic (in shares)	68,140	67,849	67,590	66,692	66,308	65,948	65,664	62,099	67,573		65,019		59,816
Diluted (in shares)	70,276	70,137	69,590	68,996	69,013	68,844	68,616	65,697	69,721		67,652		62,186
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) in accumulated other comprehensive income, net of tax expense (benefit) of $8,548, ($3,285) and $1,234 for each of the years in the three-year period ended December 31, 2019, respectively									$ 32,155		$ (12,357)		$ 2,559
Reclassification adjustment for realized (gains) losses included in net income, net of tax expense (benefit) of $9, ($27), and $73 for each of the years in the three-years ended December 31, 2019, respectively									(35)		102		(131)
Other comprehensive income (loss), net of tax									32,120		(12,255)		2,428
Comprehensive income									$ 204,077		$ 95,672		$ 24,478
[1]	Certain "Underwriting and operating expenses" have been reclassified as "Service expenses" in prior periods.

CONSOLIDATED STATEMENTS OF OP_2

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Change in unrealized investment gains (losses), tax amount	$ 8,548	$ (3,285)	$ 1,234
Reclassification adjustment from AOCI for sale of securities, tax	$ 9	$ (27)	$ 73

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands		Total	Common Stock - Class A		Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings (Accumulated Deficit)
Beginning balance at Dec. 31, 2016		$ 475,509	$ 591		$ 576,927	$ (5,287)	$ (96,722)
Beginning balance (in shares) at Dec. 31, 2016			59,145,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock: class A shares issued related to warrant exercises	[1]	$ 183			183
Common stock: class A shares issued related to warrant exercises (in shares)		32,000	32,368	[1]
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes		$ (1,480)	$ 14		(1,494)
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes (in shares)			1,341,000
Share-based compensation expense		9,484			9,484
Change in unrealized investment gains/losses, net of tax ($1,307 expense in 2019, $3,258 benefit in 2018; $8,539 expense in 2017)		2,428				2,428
Net income		22,050					22,050
Ending balance at Dec. 31, 2017		509,077	$ 605		585,488	(2,859)	(74,157)
Ending balance (in shares) at Dec. 31, 2017			60,518,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock: class A shares issued related to public offering		79,165	$ 43		79,122
Common stock: class A shares issued related to public offering (in shares)			4,255,000
Common stock: class A shares issued related to warrant exercises		$ 1,894	$ 1		1,893
Common stock: class A shares issued related to warrant exercises (in shares)		91,000	91,000
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes		$ 3,135	$ 14		3,121
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes (in shares)			1,455,000
Share-based compensation expense		12,557			12,557
Change in unrealized investment gains/losses, net of tax ($1,307 expense in 2019, $3,258 benefit in 2018; $8,539 expense in 2017)		(12,255)				(12,255)
Net income		107,927					107,927
Ending balance at Dec. 31, 2018		701,500	$ 663		682,181	(14,832)	33,488
Ending balance (in shares) at Dec. 31, 2018			66,319,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock: class A shares issued related to warrant exercises		$ 8,312	$ 3		8,309
Common stock: class A shares issued related to warrant exercises (in shares)		289,000	289,000
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes		$ 3,500	$ 18		3,482
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes (in shares)			1,750,000
Share-based compensation expense		13,031			13,031
Change in unrealized investment gains/losses, net of tax ($1,307 expense in 2019, $3,258 benefit in 2018; $8,539 expense in 2017)		32,120				32,120
Net income		171,957					171,957
Ending balance at Dec. 31, 2019		$ 930,420	$ 684		$ 707,003	$ 17,288	$ 205,445
Ending balance (in shares) at Dec. 31, 2019			68,358,000
[1]	During 2017, we issued 32,368 common shares with a par value of $0.01 in connection with the exercise of warrants, which is not identifiable in this schedule due to rounding.

CONSOLIDATED STATEMENTS OF CH_2

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in unrealized investment gains/losses, tax expense (benefit)	$ 8,539	$ (3,258)	$ 1,307
Common stock: class A shares issued related to warrant exercises (in shares)	289,000	91,000	32,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Common Stock - Class A
Common stock: class A shares issued related to warrant exercises (in shares)	289,000	91,000	32,368	[1]
[1]	During 2017, we issued 32,368 common shares with a par value of $0.01 in connection with the exercise of warrants, which is not identifiable in this schedule due to rounding.

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net income	$ 171,957	$ 107,927	$ 22,050
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized investment gains	(45)	(57)	(208)
Loss from change in fair value of warrant liability	8,657	1,397	4,105
Depreciation and amortization	9,299	7,811	6,663
Net amortization of premium on investment securities	1,252	1,519	1,599
Amortization of debt discount and debt issuance costs	1,011	3,390	1,473
Deferred income taxes	45,082	25,927	31,102
Share-based compensation expense	13,031	12,557	9,484
Changes in operating assets and liabilities:
Premiums receivable	(10,078)	(10,828)	(11,451)
Accrued investment income	(1,137)	(1,482)	(791)
Prepaid expenses	(472)	(1,090)	(160)
Deferred policy acquisition costs, net	(13,132)	(8,915)	(7,816)
Other assets	(8,831)	1,304	(1,547)
Unearned premiums	(22,251)	(4,273)	10,260
Reserve for insurance claims and claim expenses	10,941	4,050	5,760
Reinsurance balances, net	(1,022)	560	(274)
Accounts payable and accrued expenses	3,888	6,064	(2,486)
Net cash provided by operating activities	208,150	145,861	67,763
Cash flows from investing activities
Purchase of short-term investments	(230,362)	(257,916)	(131,196)
Purchase of fixed-maturity investments, available-for-sale	(290,533)	(356,337)	(219,079)
Proceeds from maturity of short-term investments	244,921	221,685	170,278
Proceeds from redemptions, maturities and sale of fixed-maturity investments, available-for-sale	91,575	179,978	95,435
Software and equipment	(9,956)	(8,060)	(8,510)
Net cash used in investing activities	(194,355)	(220,650)	(93,072)
Cash flows from financing activities
Proceeds from issuance of common stock related to public offering, net of issuance costs	0	79,165	0
Proceeds from issuance of common stock related to employee equity plans	21,748	12,857	7,103
Proceeds from issuance of common stock related to warrant exercises	0	321	183
Taxes paid related to net share settlement of equity awards	(18,248)	(9,722)	(8,582)
Proceeds from senior note, net	0	149,250	0
Repayments of term loan	(1,500)	(147,375)	(1,500)
Payments of debt issuance/modification costs	0	(3,609)	(445)
Net cash provided by (used in) financing activities	2,000	80,887	(3,241)
Net increase (decrease) in cash, cash equivalents and restricted cash	15,795	6,098	(28,550)
Cash, cash equivalents and restricted cash, beginning of period	25,294	19,196	47,746
Cash, cash equivalents and restricted cash, end of period	41,089	25,294	19,196
Supplemental disclosures of cash flow information
Interest paid	10,691	12,093	13,355
Income taxes (refunded) paid	$ (64)	$ 867	$ 1,220

Organization and Basis of Prese

Organization and Basis of Presentation	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	Organization and Basis of Presentation NMI Holdings, Inc. (NMIH) is a Delaware corporation, incorporated in May 2011 to provide private mortgage guaranty insurance (which we refer to as mortgage insurance or MI) through its wholly-owned insurance subsidiaries, National Mortgage Insurance Corporation (NMIC) and National Mortgage Reinsurance Inc One (Re One). Our common stock is listed on the NASDAQ exchange under the ticker symbol "NMIH." In April 2013, NMIC, our primary insurance subsidiary, issued its first mortgage insurance policy. NMIC is licensed to write mortgage insurance in all 50 states and the District of Columbia (D.C.) In August 2015, NMIH capitalized a wholly-owned subsidiary, NMI Services, Inc. (NMIS), through which we offer outsourced loan review services to mortgage loan originators. Basis of Presentation The accompanying consolidated financial statements include the results of NMIH and its wholly-owned subsidiaries. All inter-company transactions have been eliminated. These financial statements have been prepared in accordance with accounting principles generally accepted in the U.S. (GAAP) and our accounts are maintained in US dollars. The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect reported amounts of assets and liabilities, as well as disclosure of contingent assets and liabilities as of the balance sheet date. Estimates also affect the reported amounts of income and expenses for the reporting period. Actual results could differ from those estimates. Certain reclassifications to previously reported financial information have been made to conform to our current period presentation.

Summary of Accounting Policies

Summary of Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Summary of Accounting Principles	Summary of Accounting Principles Use of Estimates We use accounting principles and methods that conform to GAAP. We are required to apply significant judgment and make material estimates in the preparation of our financial statements and with regard to various accounting, reporting and disclosure matters. Assumptions and estimates are required to apply these principles where actual measurement is not possible or practical. Insurance Premium Revenue Recognition Premiums for primary mortgage insurance policies may be paid in a single payment at origination (single premium), on a monthly installment basis (monthly premium) or on an annual installment basis (annual premium), with such election and payment type fixed at policy inception. Premiums written at origination for single premium policies are initially deferred as unearned premiums and amortized into earnings over the estimated policy life, in accordance with the anticipated expiration of risk. Monthly premiums are recognized as revenue in the month billed and when the coverage is effective. Annual premiums are initially deferred and earned on a straight-line basis over the year of coverage. Upon cancellation of a policy, all remaining non-refundable deferred and unearned premium is immediately earned, and any refundable deferred premium is returned to the policyholder and recorded as a reduction to written premium and unearned premium reserve in the period paid. Premiums written on pool transactions are earned over the period that coverage is provided. Concentrations For the year ended December 31, 2019 , no customer accounted for more than 10% of our consolidated revenues. At December 31, 2019 , approximately 12% of our total risk-in-force (RIF) was concentrated in California. Reserves for Insurance Claims and Claim Expenses We establish reserves for claims based on our best estimate of ultimate claim costs for defaulted loans using the general principles contained in ASC 944, Financial Services - Insurance (ASC 944). We establish case reserves when we are notified that a loan has been in default for at least 60 days ( i.e ., a default) and "IBNR" reserves based on an estimate of defaults which have been incurred but have not yet been reported to us by loan servicers. We also establish reserves for claim expenses, which represent the estimated cost of the claim administration process, including legal, other third-party fees, and other general expenses of administering the claim settlement process. Claim expense reserves are either allocated ( i.e. , associated with a specific claim) or unallocated ( i.e. , not associated with a specific claim). The establishment of claims and claim expense reserves is subject to inherent uncertainty and requires significant judgment by management. Reserves are established by estimating the number of loans in default that will result in a claim payment, which is referred to as claim frequency, and the amount of the claim payment expected to be paid on each such loan in default, which is referred to as claim severity. Claim frequency and severity estimates are established based on historical observed experience regarding certain loan factors, such as age of the default, size of the loan and loan-to-value (LTV) ratios, and are strongly influenced by prevailing economic conditions, such as mortgage rates, trends in unemployment and house price appreciation. We conduct an annual actuarial review to evaluate and, if necessary, update these assumptions. Investments We have designated our investment portfolio as available-for-sale and report it at fair value. The related unrealized gains and losses, after considering the related tax expense or benefit, are recognized as a component of accumulated other comprehensive income (AOCI) (loss) in shareholders' equity. Net realized investment gains and losses are reported in income based on specific identification of securities sold or other-than-temporarily impaired, and are reclassified out of AOCI (loss). We measure fair value and classify invested assets in a hierarchy for disclosure purposes consisting of three "levels" based on the observability of inputs available in the marketplace used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). See Note 4, " Fair Value of Financial Instruments " for further discussion. Purchases and sales of investments are recorded on a trade date basis. Net investment income is recognized when earned, and includes interest and dividend income together with amortization of market premiums and discounts using the effective yield method, and is net of investment management fees and other investment related expenses. For asset-backed securities and any other holdings for which there is a prepayment risk, prepayment assumptions are evaluated and revised as necessary. Any adjustments required due to changes in effective yields and maturities are recognized on a prospective basis through yield adjustments. We evaluate our investments each quarter to determine whether declines in fair value below amortized cost are considered other-than-temporary in accordance with applicable guidance. Under the current guidance, a debt security impairment is deemed other-than-temporary if (i) we either intend to sell the security or it is more likely than not that we will be required to sell the security before recovery or (ii) we do not expect to collect cash flows sufficient to recover the amortized cost basis of the security. In evaluating whether a decline in fair value is other-than-temporary, we consider several factors including, but not limited to: • our intent to sell the security or whether it is more likely than not that we will be required to sell the security before recovery; • the severity and duration of the decline in fair value; • the financial condition of the issuer; • the failure of the issuer to make scheduled interest or principal payments; • recent credit downgrades of the applicable security or the issuer; and • adverse conditions specifically related to the security, an industry, or a geographic area. Based on this evaluation, we record OTTI adjustments on securities with declines in fair value below their amortized cost, if it is more likely than not that we will sell the securities prior to recovery of their amortized cost or if the present value of the discounted cash flows we expect to collect on the securities through recovery under a "most likely" scenario is less than their amortized cost. If our intent is to sell securities and their fair value is below amortized cost, the securities are classified as other-than-temporarily impaired and the full amount of the impairment is recognized as a loss in earnings. Otherwise, losses on other-than-temporarily impaired securities are bifurcated between credit-related losses and losses related to other factors ( e.g. , interest rate fluctuations), with credit-related losses recognized in earnings and losses related to other factors recognized in AOCI (loss), net of taxes. We consider items such as commercial paper with original maturities of 90 days or less to be short-term investments. Deferred Policy Acquisition Costs (DAC) Costs directly associated with the successful acquisition of mortgage insurance policies, consisting of certain selling expenses and other policy issuance and underwriting expenses, are initially deferred and reported as DAC. DAC is reviewed periodically to determine that it does not exceed recoverable amounts. DAC is amortized to expense in proportion to estimated gross profits over the estimated life of the associated policies. We estimate the rate of amortization to reflect actual experience and any changes to persistency or loss development. Total amortization of DAC for the years ended December 31, 2019 , 2018 and 2017 , net of a portion of ceding commission related to the quota share reinsurance transactions (see " Reinsurance ", below ) , was $8.4 million , $8.1 million and $5.8 million , respectively. Premium Deficiency Reserves We consider whether a premium deficiency exists and premium deficiency reserve is required at each fiscal quarter using best estimate assumptions as of the testing date. Per ASC 944, a premium deficiency reserve shall be recognized if the sum of expected claim costs and claim adjustment expenses, expected dividends to policyholders, unamortized acquisition costs and maintenance costs exceeds future premiums, existing reserves and anticipated investment income. We have determined that no premium deficiency reserves were necessary for any of the years in the three-year period ended December 31, 2019 . Reinsurance We account for premiums, claims and claim expenses that are ceded to reinsurers on a consistent basis with that which we use to account for the original policies we issue and pursuant to the terms of our reinsurance contracts. We account for premiums ceded or otherwise paid to reinsurers as a reduction to premium revenue. NMIC entered into quota share reinsurance treaties effective September 1, 2016 (the 2016 QSR Transaction) and January 1, 2018 (the 2018 QSR Transaction), which we refer to collectively as the QSR Transactions. We earn profit and ceding commissions in connection with the QSR Transactions (see Note 6, " Reinsurance "). Profit commissions represent a percentage of the profits recognized by reinsurers that are returned to us, based on the level of claims and claim expenses that we cede. We recognize any profit commissions we earn as an increase to premium revenue. Ceding commissions are calculated as a percentage of ceded written premiums under the 2016 QSR Transaction and as a percentage of ceded earned premiums under the 2018 QSR Transaction, and are intended to cover our costs of acquiring and servicing direct policies. We recognize any ceding commissions we earn in a manner consistent with our recognition of earnings on the underlying insurance policies, over the terms of the policies reinsured. We account for ceding commissions earned as a reduction to underwriting and operating expenses. Under the QSR Transactions, we cede a portion of claims and claim expense reserves to our reinsurers, and account for such ceded reserves as reinsurance recoverables in "Other Assets" on the consolidated balance sheets and as reductions to claims expenses on the consolidated statements of operations. We remain directly liable for all claims payments if we are unable to collect from any reinsurer. Income Taxes We account for income taxes using the liability method in accordance with ASC Topic 740, Income Taxes . The liability method measures the expected future tax effects of temporary differences at the enacted tax rates applicable for the period in which the deferred asset or liability is expected to be realized or settled. Temporary differences are differences between the tax basis of an asset or liability and its reported amount in the consolidated financial statements that would result in future increases or decreases in taxes owed on a cash basis compared to amounts already recognized as tax expense in the consolidated statement of operations. Warrants We account for warrants to purchase our common shares in accordance with ASC 470-20, Debt with Conversion and Other Options and ASC 815-40 Derivatives and Hedging - Contracts in Entity's Own Equity . Our outstanding warrants may be settled through either (i) physical settlement method, or (ii) cashless exercise, where the number of shares issued upon exercise of the warrants is reduced to cover the cost of the exercise in lieu of the holder remitting a cash payment for the exercise price. The warrants expire and are not exercisable after the 10th anniversary of the date issued. The number of warrants and exercise price are subject to anti-dilution provisions whereby the number of warrants may be increased and their exercise price may be adjusted downward under certain circumstances. The anti-dilutive adjustments may be in excess of any dilution incurred by the warrant holders, and may be triggered by events that are not dilutive. As a result, the warrants are classified as a liability. We revalue the warrants at the end of each reporting period, and any change in fair value is reported in the statements of operations in the period in which the change occurred. We calculated the fair value of the warrants using a Black-Scholes option-pricing model in combination with a binomial model. Share-Based Compensation We account for stock compensation in accordance with ASC 718, Compensation - Stock Compensation , which addresses accounting for share-based awards and recognition of compensation expense, measured using grant date fair value, over the requisite service or performance period of the award. Share-based compensation includes restricted stock units (RSUs) and stock option grants under our Stock Plans. We calculate the fair value of stock option grants using a Black-Scholes option pricing model, which takes into account various subjective assumptions. Key assumptions used in the model include the expected volatility of our stock price, dividend yield and the risk-free interest rate, as well as the expected option term, giving consideration to the contractual terms of any award. RSU grants may contain a service condition, or performance and service conditions. RSU grants are valued at our stock price on the date of grant less the present value of anticipated dividends. We account for stock option and RSU forfeitures as they occur. Earnings per Share (EPS) Basic earnings (loss) per share is based on the weighted-average number of common shares outstanding. Diluted earnings (loss) per share is based on the weighted-average number of common shares outstanding and common share equivalents that would be issuable upon the vesting of existing service based and certain performance and service based RSUs, and exercise of vested and unvested stock options and outstanding warrants. Cash and Cash Equivalents We consider items such as certificates of deposit and money market funds with original maturities of 90 days or less to be cash equivalents. Software and Equipment We capitalize certain costs associated with the development of internal-use software and equipment. Software and equipment are stated at cost, less accumulated amortization and depreciation. Amortization of software and depreciation of equipment commences at the beginning of the month following our placement of the assets into use. Amortization and depreciation are calculated on a straight-line basis over the estimated useful life of the respective assets, typically from three to five years , unless factors indicate a shorter useful life. For further detail, see Note 12, " Software and Equipment. " Business Combinations, Goodwill and Intangible Assets Goodwill represents the excess of the purchase price over the estimated fair value of net assets acquired from a business combination. In accordance with ASC 350, Intangibles - Goodwill and Other , we test goodwill for impairment during the third quarter each year, or more frequently if we believe indicators of impairment exist. We have not identified any impairments of goodwill through December 31, 2019. Our intangible assets consist of state licenses and Fannie Mae and Freddie Mac (collectively, the GSEs) applications which have indefinite lives. We test indefinite-lived intangible assets for impairment during the fourth quarter of each year or more frequently if we believe indicators of impairment exist. We have not identified any impairments of indefinite-lived intangible assets through December 31, 2019 . Premiums Receivable Premiums receivable consist of premiums due on our mortgage insurance policies. If a mortgage insurance premium is unpaid for more than 120 days, the receivable is written off against earned premium and the related insurance policy is canceled. Premiums receivable may be written off prior to 120 days in the ordinary course of business for reasons including, but not limited to, the modification or refinancing of underlying insured loans. We have established a reserve for premium write-offs based on historical experience; such reserve was deemed to be immaterial for the years ended December 31, 2019 and December 31, 2018. Variable Interest Entities NMIC is a party to reinsurance agreements with three special purpose reinsurance entities - Oaktown Re Ltd., Oaktown Re II Ltd. and Oaktown Re III Ltd. - respectively dated May 2, 2017, July 25, 2018 and July 30, 2019. At inception of the respective reinsurance agreements, we determined that Oaktown Re Ltd., Oaktown Re II, Ltd. and Oaktown Re III, Ltd, were variable interest entities (VIEs), as defined under GAAP Accounting Standards Codification (ASC) 810, because they did not have sufficient equity at risk to finance their respective activities. We evaluated the VIEs at inception to determine whether NMIC was the primary beneficiary under each deal and, if so, whether we were required to consolidate the assets and liabilities of each VIE. The primary beneficiary of a VIE is an enterprise that (1) has the power to direct the activities of the VIE, which most significantly impact its economic performance and (2) has significant economic exposure to the VIE, i.e., the obligation to absorb losses or receive benefits that could potentially be significant. The determination of whether an entity is the primary beneficiary of a VIE is complex and requires management judgment regarding determinative factors, including the expected results of the VIE and how those results are absorbed by beneficial interest holders, as well as which party has the power to direct activities that most significantly impact the performance of the VIE. We concluded that we are not the primary beneficiary of each VIE and as such, we do not consolidate them in our consolidated financial statements. See Note 6, " Reinsurance " for further discussion of the reinsurance arrangements. Recent Accounting Pronouncements - Adopted In February 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2016-02, Leases (Topic 842). This update requires that businesses recognize rights and obligations associated with certain leases as assets and liabilities on the balance sheet. The standard also requires additional disclosures regarding the amount, timing, and uncertainty of cash flows arising from leases. We adopted this ASU on January 1, 2019 using the modified-retrospective method and applied it prospectively as of the effective date, without adjusting comparative periods presented as permitted by ASU 2018-11, Leases (Topic 842), Targeted Improvements . Adoption of this new standard increased our assets and liabilities by $7.6 million in connection with the recognition of right-of-use (ROU) assets and lease liabilities, primarily related to the operating lease on our corporate headquarters. Adoption of this standard did not impact our consolidated statements of operations or cash flows. See Note 14, " Commitments and Contingencies " for additional information related to our leases. In July 2017, the FASB issued ASU 2017-11, Earnings Per Share (Topic 260), Distinguishing Liabilities from Equity (Topic 480), and Derivatives and Hedging (Topic 815). This update is intended to simplify the accounting for certain equity-linked financial instruments. We adopted this ASU on January 1, 2019. Adoption of this standard had no impact on our consolidated financial statements. In June 2018, the FASB issued ASU 2018-07, Compensation-Stock Compensation (Topic 718). This update expands the scope of Topic 718 to include share-based payments made to non-employees in connection with the acquisition of goods and services. We adopted this ASU on January 1, 2019. Adoption of this standard had no impact on our financial results as we have not made any share-based grants to non-employees as defined in ASC 718-10-20. Recent Accounting Pronouncements - Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326) and subsequently issued amendments to the initial guidance: ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments, ASU 2019-05, Financial Instruments-Credit Losses: Targeted Transition Relief, and ASU 2019-11, Codification Improvements to Topic 326, Financial Instruments-Credit Losses . These updates will require companies to measure and establish reserves for lifetime expected credit losses on many financial assets held at a given reporting date. Under the guidance, the methodology for measuring lifetime credit losses will generally shift from an incurred loss model, whereby losses are only recognized once probable and estimable, to a current expected credit loss (CECL) model, whereby losses are recognized upfront based on a future economic forecast. Credit losses relating to available-for-sale fixed maturity securities will be recorded through an allowance for credit losses, rather than a write-down of the asset as is currently required, with the amount of the allowance limited to the amount by which fair value is less than amortized cost. The length of time an available-for sale fixed maturity security has been held in an unrealized loss position will no longer impact its credit loss determination. We adopted these updates on January 1, 2020. Adoption of the updated standards did not have a material impact on our consolidated financial statements, and had no impact on our accounting for insurance claims and claim expenses as these items are not in scope of the guidance. In August 2018, the FASB issued ASU 2018-12, Targeted Improvements to the Accounting for Long-Duration Contracts . This update provides guidance to the existing recognition, measurement, presentation and disclosure requirements for long-duration contracts issued by an insurance entity. The FASB subsequently issued ASU 2019-19 in November 2019 and amended the effective date for this standard. The standard will now take effect for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2021. We are currently evaluating the impact the adoption of this ASU will have, if any, on our consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820). This update modifies the fair value measurement disclosure requirements of ASC 820. We adopted this ASU on January 1, 2020 and determined it did not have a material impact on our consolidated financial statements. In August 2018, the FASB issued ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40).This update applies to cloud computing arrangements structured as service contracts, and provides companies with guidance on the criteria for capitalizing implementation, set-up and other up-front costs incurred in association with these arrangements. We adopted this ASU on January 1, 2020 and applied it on a prospective basis for eligible costs incurred after the effective date. The adoption of this ASU did not have a material impact on our consolidated financial statements. In November 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740). This update eliminates certain exceptions for recognizing deferred taxes for investments, performing intra-period allocations and calculating income taxes in interim periods. The ASU also includes guidance to reduce complexity in certain income tax areas, including recognizing deferred taxes for tax goodwill and allocating taxes to members of a consolidated group. The standard will take effect for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020. We are currently evaluating the impact the adoption of this ASU will have, if any, on our consolidated financial statements.

Investments

Investments	12 Months Ended
	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Investments	Investments We have designated our investment portfolio as available-for-sale and report it at fair value. The related unrealized gains and losses are, after considering the related tax expense or benefit, recognized through comprehensive income and loss, and on an accumulated basis in shareholders' equity. Net realized investment gains and losses are reported in earnings based on specific identification of securities sold or other-than-temporarily impaired. Fair Values and Gross Unrealized Gains and Losses on Investments Amortized Gross Unrealized Fair Gains Losses As of December 31, 2019 (In Thousands) U.S. Treasury securities and obligations of U.S. government agencies $ 48,203 $ 784 $ (58 ) $ 48,929 Municipal debt securities 189,530 1,721 (1,035 ) 190,216 Corporate debt securities 661,719 23,373 (211 ) 684,881 Asset-backed securities 170,153 2,603 (114 ) 172,642 Total bonds 1,069,605 28,481 (1,418 ) 1,096,668 Short-term investments 44,174 98 — 44,272 Total investments $ 1,113,779 $ 28,579 $ (1,418 ) $ 1,140,940 Amortized Gross Unrealized Fair Gains Losses As of December 31, 2018 (In Thousands) U.S. Treasury securities and obligations of U.S. government agencies $ 48,171 $ 35 $ (1,376 ) $ 46,830 Municipal debt securities 92,014 206 (963 ) 91,257 Corporate debt securities 554,079 847 (11,688 ) 543,238 Asset-backed securities 171,990 792 (1,457 ) 171,325 Total bonds 866,254 1,880 (15,484 ) 852,650 Short-term investments 58,733 107 — 58,840 Total investments $ 924,987 $ 1,987 $ (15,484 ) $ 911,490 We did not own any mortgage-backed securities in our asset-backed securities portfolio at December 31, 2019 or 2018 . The following table presents a breakdown of the fair value of our corporate debt securities by issuer industry group as of December 31, 2019 and 2018 : December 31, 2019 December 31, 2018 Financial 38 % 38 % Consumer 26 27 Communications 10 12 Utilities 9 7 Industrial 8 7 Technology 7 6 Energy 2 2 Other — 1 Total 100 % 100 % As of December 31, 2019 and 2018, approximately $5.5 million and $5.3 million , respectively, of our cash and investments were held in the form of U.S. Treasury securities on deposit with various state insurance departments to satisfy regulatory requirements. Scheduled Maturities The amortized cost and fair values of available-for-sale securities as of December 31, 2019 and 2018, by contractual maturity, are shown below. Expected maturities will differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. Because most asset-backed securities provide for periodic payments throughout their lives, they are listed below in a separate category. As of December 31, 2019 Amortized Fair (In Thousands) Due in one year or less $ 138,776 $ 139,113 Due after one through five years 406,986 417,208 Due after five through ten years 380,737 394,180 Due after ten years 17,127 17,797 Asset-backed securities 170,153 172,642 Total investments $ 1,113,779 $ 1,140,940 As of December 31, 2018 Amortized Fair (In Thousands) Due in one year or less $ 76,087 $ 76,104 Due after one through five years 352,282 347,701 Due after five through ten years 318,728 310,633 Due after ten years 5,900 5,727 Asset-backed securities 171,990 171,325 Total investments $ 924,987 $ 911,490 Aging of Unrealized Losses As of December 31, 2019 , the investment portfolio had gross unrealized losses of $1.4 million , of which $0.1 million had been in an unrealized loss position for a period of 12 months or greater. We did not consider these securities to be other-than-temporarily impaired as of December 31, 2019 . We based our conclusion that these investments were not other-than-temporarily impaired as of December 31, 2019 on the following facts: (i) the unrealized losses were primarily caused by interest rate movements and market fluctuations in credit spreads since the purchase date, (ii) we do not intend to sell these investments; and (iii) we do not believe that it is more likely than not that we will be required to sell these investments before recovery of our amortized cost basis, which may not occur until maturity. For those securities in an unrealized loss position, the length of time the securities were in such a position is as follows: Less Than 12 Months 12 Months or Greater Total # of Securities Fair Value Unrealized Losses # of Securities Fair Value Unrealized Losses # of Securities Fair Value Unrealized Losses As of December 31, 2019 (Dollars in Thousands) U.S. Treasury securities and obligations of U.S. government agencies 4 $ 12,001 $ (58 ) — $ — $ — 4 $ 12,001 $ (58 ) Municipal debt securities 26 92,844 (1,034 ) 1 999 (1 ) 27 93,843 (1,035 ) Corporate debt securities 10 30,481 (140 ) 14 23,976 (71 ) 24 54,457 (211 ) Asset-backed securities 9 19,236 (102 ) 1 2,988 (12 ) 10 22,224 (114 ) Total 49 $ 154,562 $ (1,334 ) 16 $ 27,963 $ (84 ) 65 $ 182,525 $ (1,418 ) Less Than 12 Months 12 Months or Greater Total # of Securities Fair Value Unrealized Losses # of Securities Fair Value Unrealized Losses # of Securities Fair Value Unrealized Losses As of December 31, 2018 (Dollars in Thousands) U.S. Treasury securities and obligations of U.S. government agencies — $ — $ — 19 $ 41,817 $ (1,376 ) 19 $ 41,817 $ (1,376 ) Municipal debt securities 4 7,409 (11 ) 31 58,658 (952 ) 35 66,067 (963 ) Corporate debt securities 118 226,477 (3,952 ) 126 221,675 (7,736 ) 244 448,152 (11,688 ) Asset-backed securities 25 36,017 (1,136 ) 22 33,988 (321 ) 47 70,005 (1,457 ) Total 147 $ 269,903 $ (5,099 ) 198 $ 356,138 $ (10,385 ) 345 $ 626,041 $ (15,484 ) Net Investment Income The following table presents the components of net investment income: For the year ended December 31, 2019 2018 2017 (In Thousands) Investment income $ 31,332 $ 24,342 $ 17,046 Investment expenses (476 ) (804 ) (773 ) Net investment income $ 30,856 $ 23,538 $ 16,273 The following table presents the components of net realized investment gains: For the year ended December 31, 2019 2018 2017 (In Thousands) Gross realized investment gains $ 561 $ 525 $ 546 Gross realized investment losses (516 ) (468 ) (338 ) Net realized investment gains $ 45 $ 57 $ 208 Investment Securities - Other-than-Temporary Impairment (OTTI) As of December 31, 2019 , 2018 and 2017 , we held no other-than-temporarily impaired securities. For the years ended December 31, 2019 and 2017, we recognized $0.4 million and $0.1 million of OTTI losses in earnings, respectively. For the year ended December 31, 2018 we did no t recognize any OTTI losses. There were no credit losses recognized in earnings for which a portion of an OTTI loss was recognized in AOCI (loss) for any period presented.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments The following describes the valuation techniques used by us to determine the fair value of our financial instruments: We established a fair value hierarchy by prioritizing the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy under this standard are described below: Level 1 - Fair value measurements based on quoted prices in active markets that we have the ability to access for identical assets or liabilities. Market price data generally is obtained from exchange or dealer markets. We do not adjust the quoted price for such instruments. Level 2 - Fair value measurements based on inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, and inputs other than quoted prices that are observable for the asset or liability, such as interest rates and yield curves that are observable at commonly quoted intervals. Level 3 - Fair value measurements based on valuation techniques that use significant inputs that are unobservable. Both observable and unobservable inputs may be used to determine the fair values of positions classified in Level 3. The circumstances for using these measurements include those in which there is little, if any, market activity for the asset or liability. Therefore, we must make certain assumptions, which require significant management judgment or estimation about the inputs a hypothetical market participant would use to value that asset or liability. In certain cases, the inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, the level in the fair value hierarchy is determined based on the lowest level input that is significant to the fair value measurement in its entirety. Assets classified as Level 1 and Level 2 To determine the fair value of securities available-for-sale in Level 1 and Level 2 of the fair value hierarchy, independent pricing sources have been utilized. One price is provided per security based on observable market data. To ensure securities are appropriately classified in the fair value hierarchy, we review the pricing techniques and methodologies of the independent pricing sources 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. A variety of inputs are utilized by the independent pricing sources including benchmark yields, reported trades, non-binding broker/dealer quotes, issuer spreads, two sided markets, benchmark securities, bids, offers and reference data including data published in market research publications. Inputs may be weighted differently for any security, and not all inputs are used for each security evaluation. Market indicators, industry and economic events are also considered. This information is evaluated using a multidimensional pricing model. Quality controls are performed by the independent pricing sources throughout this process, which include reviewing tolerance reports, trading information and data changes, and directional moves compared to market moves. This model combines all inputs to arrive at a value assigned to each security. We have not made any adjustments to the prices obtained from the independent pricing sources. Liabilities classified as Level 3 We calculate the fair value of outstanding warrants utilizing Level 3 inputs, including a Black-Scholes option-pricing model, in combination with a binomial model, and we value the pricing protection features within the warrants using a Monte-Carlo simulation model. Variables in the model include the risk-free rate of return, dividend yield, expected life and expected volatility of our stock price. The following tables present the level within the fair value hierarchy at which our financial instruments were measured: Fair Value Measurements Using Quoted Prices in Significant Other Significant Fair Value As of December 31, 2019 (In Thousands) U.S. Treasury securities and obligations of U.S. government agencies $ 48,929 $ — $ — $ 48,929 Municipal debt securities — 190,216 — 190,216 Corporate debt securities — 684,881 — 684,881 Asset-backed securities — 172,642 — 172,642 Cash, cash equivalents and short-term investments 85,361 — — 85,361 Total assets $ 134,290 $ 1,047,739 $ — $ 1,182,029 Warrant liability — — 7,641 7,641 Total liabilities $ — $ — $ 7,641 $ 7,641 Fair Value Measurements Using Quoted Prices in Significant Other Significant Fair Value As of December 31, 2018 (In Thousands) U.S. Treasury securities and obligations of U.S. government agencies $ 46,830 $ — $ — $ 46,830 Municipal debt securities — 91,257 — 91,257 Corporate debt securities — 543,238 — 543,238 Asset-backed securities — 171,325 — 171,325 Cash, cash equivalents and short-term investments 84,134 — — 84,134 Total assets $ 130,964 $ 805,820 $ — $ 936,784 Warrant liability — — 7,296 7,296 Total liabilities $ — $ — $ 7,296 $ 7,296 There were no transfers between Level 1 and Level 2, nor any transfers in or out of Level 3, of the fair value hierarchy during the years ended December 31, 2019 or 2018 . The following is a roll-forward of Level 3 liabilities measured at fair value: For the year ended December 31, 2019 2018 2017 (In Thousands) Balance, January 1 $ 7,296 $ 7,472 $ 3,367 Change in fair value of warrant liability included in earnings 8,657 1,397 4,105 Issuance of common stock on warrant exercise (8,312 ) (1,573 ) — Balance, December 31 $ 7,641 $ 7,296 $ 7,472 The following table outlines the key inputs and assumptions used to calculate the fair value of the warrant liability in the Black-Scholes option-pricing model as of the dates indicated. As of December 31, 2019 2018 2017 Common stock price $ 33.18 $ 17.85 $ 17.00 Risk free interest rate 1.59 % 2.46 - 2.47% 1.99 % Expected life 2.31 years 2.58 - 3.31 years 3.07 years Expected volatility 41.4 % 41.1 - 42.5% 30.6 % Dividend yield — % — % — % The changes in fair value of the warrant liability for the years ended December 31, 2019 , 2018 , and 2017 are primarily attributable to changes in the price of our common stock and exercises of outstanding warrants during the respective periods, with additional impact related to changes in other Black-Scholes model inputs. Financial Instruments not Measured at Fair Value At December 31, 2019 , our 2018 Term Loan was carried at a cost of $145.8 million , net of debt issuance costs of $2.0 million , and had a fair value of $147.8 million as assessed under our Level 2 hierarchy. At December 31, 2018, our 2018 Term Loan was carried at a cost of $146.8 million , net of debt issuance costs of $2.5 million , and had a fair value of $146.3 million .

Debt

Debt	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Debt	Debt On May 24, 2018, we entered into a credit agreement (2018 Credit Agreement), which provides for (i) a $150 million 5-year senior secured term loan facility (2018 Term Loan) that matures on May 24, 2023; and (ii) a $85 million three-year secured revolving credit facility (2018 Revolving Credit Facility) that matures on May 24, 2021. Proceeds from the 2018 Term Loan were used to repay in full the outstanding amount due under our $150 million amended term loan (2015 Term Loan) due on November 10, 2019, and to pay fees and expenses incurred in connection with the 2018 Credit Agreement. 2018 Term Loan The 2018 Term Loan bears interest at the LIBOR, as defined in the 2018 Credit Agreement and subject to a 1.00% floor, plus an annual margin rate of 4.75% , representing an all-in rate of 6.55% as of December 31, 2019 , payable monthly based on our current interest period election. Quarterly principal payments of $0.4 million are also required. As of December 31, 2019 , the outstanding principal balance of the 2018 Term Loan was $147.8 million . Interest expense for the 2018 Term Loan includes interest and the amortization of issuance costs, an original issue discount and capitalized modification costs related to the 2015 Term Loan. For the year ended December 31, 2019 , we recorded $11.2 million of interest expense. Remaining unamortized issuance costs and original issue discount were $2.0 million as of December 31, 2019 and are being amortized to interest expense using the effective interest method over the contractual life of the 2018 Term Loan. We are subject to certain covenants under the 2018 Term Loan (as defined in the 2018 Credit Agreement), including (but not limited to) a maximum debt-to-total capitalization ratio (as defined in the 2018 Credit Agreement) of 35% under the 2018 Term Loan. We were in compliance with all covenants as of December 31, 2019 . Future principal payments due under the 2018 Term Loan as of December 31, 2019 are as follows: As of December 31, 2019 Principal (In thousands) 2020 $ 1,500 2021 1,500 2022 1,500 2023 143,250 Total $ 147,750 2018 Revolving Credit Facility Borrowings under the 2018 Revolving Credit Facility may be used for general corporate purposes and will accrue interest at a variable rate equal to, at our discretion, (i) a base rate (as defined in the 2018 Credit Agreement, subject to a floor of 1.00% per annum) plus a margin of 1.00% to 2.50% per annum, based on the applicable corporate credit rating at the time, or (ii) the Eurodollar Rate (subject to a floor of 0.00% per annum) plus a margin of 2.00% to 3.50% per annum, based on the applicable corporate credit rating at the time. As of December 31, 2019 , no borrowings had been made under the 2018 Revolving Credit Facility. We are required to pay a quarterly commitment fee on the average daily undrawn amount of the 2018 Revolving Credit Facility, which ranges from 0.30% to 0.60% , based on the applicable corporate credit rating at the time. As of December 31, 2019 , the applicable commitment fee was 0.40% . For the year ended December 31, 2019 , we recorded $0.4 million of commitment fees in interest expense. We incurred issuance costs of $1.5 million in connection with the establishment of the 2018 Revolving Credit Facility, which were deferred and recorded within "Other assets." These costs are being amortized through interest expense over the three-year life of the 2018 Revolving Credit Facility on a straight line basis. For the year ended December 31, 2019 , we recognized $0.5 million of interest expense from the amortization of deferred issuance costs. At December 31, 2019 , remaining deferred issuance costs were $0.7 million , net of accumulated amortization. We are subject to certain covenants under the 2018 Revolving Credit Facility, including (but not limited to) the following: a maximum debt-to-total capitalization ratio of 35% , a minimum liquidity requirement, compliance with the private mortgage insurer eligibility requirements (PMIERs) financial requirements (subject to any GSE-approved waivers), and minimum consolidated net worth and statutory capital requirements (respectively, as defined therein). We were in compliance with all covenants as of December 31, 2019 .

Reinsurance

Reinsurance	12 Months Ended
	Dec. 31, 2019
Reinsurance Disclosures [Abstract]
Reinsurance	Reinsurance We enter into third-party reinsurance transactions to actively manage our risk, ensure compliance with PMIERs, state regulatory and other applicable capital requirements, and support the growth of our business. The GSEs and the Wisconsin Office of the Commissioner of Insurance (Wisconsin OCI) have approved all such transactions (subject to certain conditions and ongoing review, including levels of approved capital credit). The effect of our reinsurance agreements on premiums written and earned is as follows: For the year ended December 31, 2019 December 31, 2018 December 31, 2017 (In Thousands) Net premiums written Direct $ 376,052 $ 287,791 $ 202,586 Ceded (1) (43,400 ) (30,988 ) (28,914 ) Net premiums written $ 332,652 $ 256,803 $ 173,672 Net premiums earned Direct $ 398,303 $ 292,064 $ 192,326 Ceded (1) (53,288 ) (40,867 ) (26,586 ) Net premiums earned $ 345,015 $ 251,197 $ 165,740 (1) Net of profit commission. Excess-of-loss reinsurance NMIC entered into excess-of-loss reinsurance agreements with Oaktown Re Ltd., Oaktown Re II Ltd. and Oaktown Re III Ltd. (special purpose reinsurance entities collectively referred to as the Oaktown Re Vehicles) effective May 2, 2017, July 25, 2018 and July 30, 2019, respectively. Each agreement provides NMIC with aggregate excess-of-loss reinsurance coverage on a defined portfolio of mortgage insurance policies written during a discrete period. Under each agreement, NMIC retains a first layer of aggregate loss exposure on covered policies and the respective Oaktown Re Vehicle then provides second layer loss protection up to a defined reinsurance coverage amount. NMIC then retains losses in excess of the respective reinsurance coverage amounts. The respective reinsurance coverage amounts provided by the Oaktown Re Vehicles decrease from the inception of each agreement over a 10 year period as the underlying insured mortgages are amortized or repaid, and/or the mortgage insurance coverage is canceled. The respective outstanding reinsurance coverage amounts stop amortizing if certain credit enhancement or delinquency thresholds, as defined in each agreement, are triggered. NMIC makes risk premium payments to the Oaktown Re Vehicles for the applicable outstanding reinsurance coverage amount and pays an additional amount for anticipated operating expenses (capped at $300 thousand per year to Oaktown Re Ltd. and $250 thousand per year to Oaktown Re II, Ltd. and Oaktown Re III, Ltd.). NMIC ceded aggregate premiums to the Oaktown Re Vehicles of $14.6 million , $9.6 million and $5.0 million during the years ended December 31, 2019 , 2018 and 2017 , respectively. NMIC applies claims paid on covered policies against its first layer aggregate retained loss exposure under each excess-of-loss agreement. NMIC did not cede any incurred losses on covered policies to the Oaktown Re Vehicles during the years ended December 31, 2019, 2018 or 2017, as the aggregate first layer risk retention was not exhausted for each applicable agreement during such periods. Under the terms of each excess-of-loss reinsurance agreement, the Oaktown Re Vehicles are required to fully collateralize their outstanding reinsurance coverage amount to NMIC with funds deposited into segregated reinsurance trusts. Such trust funds are required to be invested in short-term U.S. Treasury money market funds at all times. Each Oaktown Re Vehicle financed its respective collateral requirement through the issuance of mortgage insurance-linked notes to unaffiliated investors. Such insurance-linked notes mature 10 years from the inception date of each reinsurance agreement. We refer to NMIC's reinsurance agreements with and the insurance-linked note issuances by Oaktown Re Ltd., Oaktown Re II, Ltd. and Oaktown Re III, Ltd. individually as the 2017 ILN Transaction, 2018 ILN Transaction and 2019 ILN Transaction, and collectively as the ILN Transactions. The following table presents the inception date, covered production period, initial and current reinsurance coverage amount, and initial and current first layer retained aggregate loss under each of the ILN Transactions. ( $ values in thousands) Inception Date Covered Production Initial Reinsurance Coverage Current Reinsurance Coverage Initial First Layer Retained Loss Current First Layer Retained Loss 2017 ILN Transaction May 2, 2017 1/1/2013 - 12/31/2016 $ 211,320 $ 61,900 $ 126,793 $ 123,330 2018 ILN Transaction July 25, 2018 1/1/2017 - 5/31/2018 264,545 202,396 125,312 124,594 2019 ILN Transaction July 30, 2019 6/1/2018 - 6/30/2019 326,905 301,396 123,424 123,424 NMIC holds optional termination rights under each ILN Transaction, including, among others, an optional call feature which provides NMIC the discretion to terminate the transaction on or after a prescribed date, and a clean-up call if the outstanding reinsurance coverage amount amortizes to 10% or less of the reinsurance coverage amount at inception or if NMIC reasonably determines that changes to GSE or rating agency asset requirements would cause a material and adverse effect on the capital treatment afforded to NMIC under a given agreement. In addition, there are certain events that trigger mandatory termination of an agreement, including NMIC's failure to pay premiums or consent to reductions in a trust account to make principal payments to noteholders, among others. Under the terms of the 2018 ILN Transaction and the 2019 ILN Transaction, we are required to maintain a certain level of restricted funds in premium deposit accounts with Bank of New York Mellon until the respective notes have been redeemed in full. "Cash and cash equivalents" on our condensed consolidated balance sheet includes restricted amounts of $2.7 million as of December 31, 2019 . We are not required to deposit additional funds into the premium deposit accounts in the future and the restricted balances required under these transactions will decrease over time as the outstanding principal balances of the respective insurance-linked notes decline. Quota share reinsurance Under each of the QSR Transactions, NMIC cedes a proportional share of its risk on eligible policies written during a discrete period to panels of third-party reinsurance providers. Each of the third-party reinsurance providers has an insurer financial strength rating of A- or better by Standard & Poor's Rating Service (S&P), A.M. Best Company, Inc. (A.M. Best) or both. Under the 2016 QSR Transaction, NMIC cedes premiums written related to 25% of the risk on eligible primary policies written for all periods through December 31, 2017 and 100% of the risk under our pool agreement with Fannie Mae. The 2016 QSR Transaction is scheduled to terminate on December 31, 2027, except with respect to the ceded pool risk, which is scheduled to terminate on August 31, 2023. NMIC has the option, based on certain conditions and subject to a termination fee, to terminate the agreement as of December 31, 2020, or at the end of any calendar quarter thereafter, which would result in NMIC reassuming the related risk. Under the 2018 QSR Transaction, NMIC cedes premiums earned related to 25% of the risk on eligible policies written in 2018 and 20% of the risk on eligible policies written in 2019. The 2018 QSR Transaction is scheduled to terminate on December 31, 2029. NMIC has the option, based on certain conditions and subject to a termination fee, to terminate the agreement as of December 31, 2022, or at the end of any calendar quarter thereafter, which would result in NMIC reassuming the related risk. NMIC may terminate either or both of the QSR Transactions without penalty if, due to a change in PMIERs requirements, it is no longer able to take full PMIERs asset credit for the RIF ceded under the respective agreements. Additionally, under the terms of the QSR Transactions, NMIC may elect to selectively terminate its engagement with individual reinsurers on a run-off basis ( i.e. , reinsurers continue providing coverage on all risk ceded prior to the termination date, with no new cessions going forward) or cut-off basis ( i.e. , the reinsurance arrangement is completely terminated with NMIC recapturing all previously ceded risk) under certain circumstances. Such selective termination rights arise when, among other reasons, a reinsurer experiences a deterioration in its capital position below a prescribed threshold and/or a reinsurer breaches (and fails to cure) its collateral posting obligations under the relevant agreement. Effective April 1, 2019, NMIC elected to terminate its engagement with one reinsurer under the 2016 QSR Transaction on a cut-off basis. In connection with the termination, NMIC recaptured approximately $500 million of previously ceded primary RIF and stopped ceding new premiums earned or written with respect to the recaptured risk. With the termination, ceded premiums written under the 2016 QSR Transaction decreased from 25% to 20.5% on eligible policies. The termination has no effect on the cession of pool risk under the 2016 QSR Transaction. The following table shows the amounts related to the QSR Transactions: For the year ended December 31, 2019 December 31, 2018 December 31, 2017 (In Thousands) Ceded risk-in-force $ 5,137,249 $ 4,292,450 $ 2,983,353 Ceded premiums earned (89,211 ) (74,068 ) (49,619 ) Ceded claims and claim expenses 3,465 1,763 1,687 Ceding commission earned 17,652 14,585 9,806 Profit commission 50,513 42,846 28,084 Ceded premiums written under the 2016 QSR Transaction are recorded on the balance sheet as prepaid reinsurance premiums and amortized to ceded premiums earned in a manner consistent with the recognition of revenue on direct premiums. Under the 2018 QSR Transaction, premiums are ceded on an earned basis as defined in the agreement. NMIC receives a 20% ceding commission for premiums ceded under the QSR Transactions. NMIC also receives a profit commission under each of the QSR Transactions, provided that the loss ratios on loans covered under the 2016 QSR Transaction and 2018 QSR Transaction generally remain below 60% and 61% , respectively, as measured annually. Ceded claims and claim expenses under each of the QSR Transactions reduce the respective profit commission received by NMIC on a dollar-for-dollar basis. In accordance with the terms of the 2016 QSR Transaction, rather than making a cash payment or transferring investments for ceded premiums written, NMIC established a funds withheld liability, which also includes amounts due to NMIC for ceding and profit commissions. Any loss recoveries and any potential profit commission to NMIC will be realized from this account until exhausted. NMIC's reinsurance recoverable balance is further supported by trust accounts established and maintained by each reinsurer in accordance with the PMIERs funding requirements for risk ceded to non-affiliates. The reinsurance recoverable on loss reserves related to our 2016 QSR Transaction was $2.8 million as of December 31, 2019 . In accordance with the terms of the 2018 QSR Transaction, cash payments for ceded premiums earned are settled on a quarterly basis, offset by amounts due to NMIC for ceding and profit commissions. Any loss recoveries and any potential profit commission to NMIC are also settled quarterly. NMIC's reinsurance recoverable balance is supported by trust accounts established and maintained by each reinsurer in accordance with the PMIERs funding requirements for risk ceded to non-affiliates. The reinsurance recoverable on loss reserves related to our 2018 QSR Transaction was $2.1 million as of December 31, 2019 .

Reserve for Insurance Claims an

Reserve for Insurance Claims and Claim Expenses	12 Months Ended
	Dec. 31, 2019
Insurance [Abstract]
Reserves for Insurance Claims and Claim Expenses	Reserves for Insurance Claims and Claim Expenses We establish reserves to recognize the estimated liability for insurance claims and claim expenses related to defaults on insured mortgage loans. Consistent with industry practice, we establish reserves for loans that have been reported to us by servicers as having been in default for at least 60 days, referred to as case reserves, and additional loans that we estimate (based on actuarial review) have been in default for at least 60 days that have not yet been reported to us by servicers, referred to as "IBNR" reserves. We also establish claim expense reserves, which represent the estimated cost of the claim administration process, including legal and other fees, as well as other general expenses of administering the claims settlement process. As of December 31, 2019 , we had reserves for insurance claims and claim expenses of $23.8 million for 1,448 primary loans in default. During the year ended December 31, 2019 , we paid 152 claims totaling $5.0 million , including 142 claims covered under the QSR Transactions representing $1.0 million of ceded claims and claim expenses. In 2013, we entered into a pool insurance transaction with Fannie Mae. The pool transaction includes a deductible, which represents the amount of claims to be absorbed by Fannie Mae before we are obligated to pay any claims. We only establish reserves for pool risk if we expect claims to exceed this deductible. At December 31, 2019 , 46 loans in the pool were past due by 60 days or more. These 46 loans represented approximately $3.0 million of RIF. Due to the size of the remaining deductible, the low level of notices of defaults (NODs) reported on loans in the pool through December 31, 2019 and the expected severity (all loans in the pool have LTV ratios under 80% ), we did not establish any case or IBNR reserves for pool risk at December 31, 2019 . In connection with the settlement of pool claims, we applied $0.8 million to the pool deductible through December 31, 2019 . At December 31, 2019 , the remaining pool deductible was $9.5 million . We have not paid any pool claims to date. 100% of our pool RIF is reinsured under the 2016 QSR Transaction. The following table provides a reconciliation of the beginning and ending reserve balances for primary insurance claims and claim expenses: For the year ended December 31, 2019 December 31, 2018 December 31, 2017 (In Thousands) Beginning balance $ 12,811 $ 8,761 $ 3,001 Less reinsurance recoverables (1) (3,001 ) (1,902 ) (297 ) Beginning balance, net of reinsurance recoverables 9,810 6,859 2,704 Add claims incurred: Claims and claim expenses incurred: Current year (2) 14,737 7,860 6,140 Prior years (3) (2,230 ) (2,408 ) (801 ) Total claims and claim expenses incurred 12,507 5,452 5,339 Less claims paid: Claims and claim expenses paid: Current year (2) 204 130 27 Prior years (3) 3,849 2,371 1,157 Reinsurance terminations (4) (549 ) — — Total claims and claim expenses paid 3,504 2,501 1,184 Reserve at end of period, net of reinsurance recoverables 18,813 9,810 6,859 Add reinsurance recoverables (1) 4,939 3,001 1,902 Ending balance $ 23,752 $ 12,811 $ 8,761 (1) Related to ceded losses recoverable under the QSR Transactions, included in "Other assets" on the Consolidated Balance Sheets. See Note 6, " Reinsurance " for additional information. (2) Related to insured loans with their most recent defaults occurring in the current year. For example, if a loan defaulted in a prior year and subsequently cured and later re-defaulted in the current year, the default would be included in the current year. Amounts are presented net of reinsurance. (3) Related to insured loans with defaults occurring in prior years, which have been continuously in default before the start of the current year. Amounts are presented net of reinsurance. (4) Represents the settlement of reinsurance recoverables in conjunction with the termination of one reinsurer under the 2016 QSR Transaction on a cut-off basis. See Note 6, " Reinsurance " for additional information. The "claims incurred" section of the table above shows claims and claim expenses incurred on NODs for current and prior years, including IBNR reserves and is presented net of reinsurance. The amount of claims incurred relating to current year NODs represents the estimated amount of claims and claim expenses to be ultimately paid on such loans in default. We recognized $2.2 million , $2.4 million , and $0.8 million of favorable prior year development during the years ended December 31, 2019 , 2018 and 2017 , respectively, due to NOD cures and ongoing analysis of recent loss development trends. We may increase or decrease our original estimates as we learn additional information about individual defaults and claims and continue to observe and analyze loss development trends in our portfolio. Gross reserves of $5.2 million related to prior year defaults remained as of December 31, 2019 . The following tables provide claim development data, by accident year and a reconciliation to the reserve for insurance claims and claim expenses. Cumulative Incurred Claims and Allocated Claims Adjustment Expenses, net of Reinsurance (1) As of December 31, 2019 Accident Year 2013 2014 2015 2016 2017 2018 2019 Total of IBNR NODs (2) ($ Values In Thousands) 2013 $ — $ — $ — $ — $ — $ — $ — $ — — 2014 83 34 4 4 4 4 2015 699 664 743 764 894 1 1 2016 2,394 1,568 1,790 1,934 4 5 2017 6,028 3,475 3,570 30 34 2018 7,779 5,271 155 174 2019 14,391 $ 1,097 1,234 Total $ 26,064 $ 1,287 1,448 (1) Amounts include case and IBNR reserves. (2) The number of NODs outstanding as of December 31, 2019 is the total number of loans in default over 60 days. Cumulative Paid Claims and Claims Adjustment Expenses, net of Reinsurance Accident Year 2013 2014 2015 2016 2017 2018 2019 (In Thousands) 2013 $ — $ — $ — $ — $ — $ — $ — 2014 — 4 4 4 4 4 2015 50 246 684 720 804 2016 171 890 1,596 1,826 2017 27 1,655 2,925 2018 130 1,981 2019 69 Total $ 7,609 Reconciliation of Disclosure of Incurred and Paid Claims Development to the Liability for Unpaid Claims and Claim Adjustment Expenses (In Thousands) As of December 31, 2019 Cumulative Incurred Claims and Allocated Claims Adjustment Expenses, net of Reinsurance $ 26,064 Cumulative Paid Claims and Claims Adjustment Expenses, net of Reinsurance 7,609 Liabilities for unpaid claims and allocated claims adjustment expenses, net of reinsurance 18,455 Reinsurance recoverable on unpaid claims 4,939 Unallocated claims adjustment expenses 358 Total gross liability for unpaid claims and claim adjustment expenses $ 23,752 The following table shows, on average, the percentage of claims and allocated claims adjustment expenses paid over the years after a claim is incurred. Average annual percentage payout of incurred claims and allocated claims adjustment expenses by age, net of reinsurance Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Claims duration disclosure 3% 38% 91% 96% 95% 100%

Earnings per Share

Earnings per Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Earnings per Share	Earnings per Share Basic EPS is based on the weighted average number of shares of common stock outstanding. Diluted EPS is based on the weighted average number of shares of common stock outstanding and common stock equivalents that would be issuable upon the vesting of service based and performance and service based RSUs, and the exercise of vested and unvested stock options and outstanding warrants. The number of shares issuable for RSUs subject to performance and service based vesting requirements are only included in diluted shares if the relevant performance measurement period has commenced and results during such period meet the necessary performance criteria. The following table reconciles the net income and the weighted average shares of common stock outstanding used in the computations of basic and diluted EPS of common stock. For the year ended December 31, 2019 2018 2017 (In Thousands, except for per share data) Net income $ 171,957 $ 107,927 $ 22,050 Basic weighted average shares outstanding 67,573 65,019 59,816 Basic earnings per share $ 2.54 $ 1.66 $ 0.37 Net income $ 171,957 $ 107,927 $ 22,050 Gain from change in fair value of warrant liability — — — Diluted net income $ 171,957 $ 107,927 $ 22,050 Basic weighted average shares outstanding 67,573 65,019 59,816 Dilutive effect of issuable shares 2,148 2,633 2,370 Diluted weighted average shares outstanding 69,721 67,652 62,186 Diluted earnings per share $ 2.47 $ 1.60 $ 0.35 Anti-dilutive shares 565 843 995

Warrants

Warrants	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Warrants	Warrants We issued 992 thousand warrants in connection with a private placement of our common stock in April 2012. Each warrant gives the holder thereof the right to purchase one share of common stock at an exercise price equal to $10.00 . The warrants were issued with an aggregate fair value of $5.1 million . During the year ended December 31, 2019 , 448 thousand warrants were exercised resulting in the issuance of 289 thousand shares of common stock. Upon exercise, we reclassified approximately $8.3 million of warrant fair value from warrant liability to additional paid-in capital, of which $4.1 million related to changes in fair value during the twelve months ended December 31, 2019 . During the year ended December 31, 2018 , 151 thousand warrants were exercised resulting in the issuance of 91 thousand shares of common stock. Upon exercise, we reclassified approximately $1.6 million of warrant fair value from warrant liability to additional paid-in capital, of which $0.4 million related to changes in fair value during the twelve months ended December 31, 2018 . During the year ended December 31, 2017 , 55 thousand warrants were exercised resulting in the issuance of 32 thousand

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Share-Based Compensation	Share-Based Compensation Share-based compensation includes stock options and RSUs granted under our 2012 Stock Incentive Plan (2012 Plan) and our Amended and Restated 2014 Omnibus Incentive Plan (2014 Plan, and together with the 2012 Plan, the Stock Plans). The 2012 Plan was approved by the Board on April 16, 2012 and authorized 5.5 million shares of common stock to be reserved for issuance, with limits of 3.85 million shares available for stock option issuance and 1.65 million shares available for RSU issuance. Options granted under the 2012 Plan are non-qualified stock options and may be granted to employees, directors and other key persons. The exercise price per share for options covered by the 2012 Plan is determined by the Board at the time of grant, but shall not be less than the fair market value of our common stock, defined as the closing price of our common stock, on the date of the grant. The term of the stock option grants is established by the Board, but no stock option shall be exercisable more than ten years after the date the stock option is granted. The vesting period of the stock option grants is also established by the Board at the time of grant and is generally a three -year period. Upon the exercise of stock options, we issue shares from the authorized, unissued share reserve. The 2014 Plan was originally approved by our stockholders at our annual meeting on May 8, 2014 and authorized 4.0 million shares of common stock to be reserved for issuance. On May 11, 2017, our stockholders approved amendments to the 2014 Plan at our annual stockholder meeting, authorizing an additional 2.0 million shares of common stock for issuance, increasing the total shares of common stock reserved for issuance under the plan to 6.0 million . These shares may be either authorized but unissued shares or treasury shares. For the years ended December 31, 2019 , 2018 and 2017 , we incurred $13.0 million , $12.6 million and $9.5 million , respectively, of expenses related to awards granted under our Stock Plans. We recognized related income tax benefits of $2.7 million , $2.6 million and $2.0 million for the years ended December 31, 2019 , 2018 and 2017 , respectively. A summary of option activity during the years ended December 31, 2019 , 2018 and 2017 , is as follows: For the year ended December 31, 2019 Shares Weighted Average Grant Date Fair Value per Share Weighted Average Exercise Price (Shares in Thousands) Options outstanding at December 31, 2018 2,882 $ 4.24 $ 11.42 Options granted 163 8.85 22.19 Options exercised (1,117 ) 3.88 10.19 Options forfeited — — — Options expired — — — Options outstanding at December 31, 2019 1,928 $ 4.84 $ 13.04 For the Year Ended December 31, 2018 Shares Weighted Average Grant Date Fair Value per Share Weighted Average Exercise Price (Shares in Thousands) Options outstanding at December 31, 2017 3,311 $ 3.95 $ 10.41 Options granted 383 6.32 18.08 Options exercised (803 ) 4.06 10.43 Options forfeited — — — Options expired (9 ) 4.05 10.51 Options outstanding at December 31, 2018 2,882 $ 4.24 $ 11.42 For the year ended December 31, 2017 Shares Weighted Average Grant Date Fair Value per Share Weighted Average Exercise Price (Shares in Thousands) Options outstanding at December 31, 2016 3,026 $ 3.97 $ 10.27 Options granted 574 3.89 11.06 Options exercised (273 ) 3.93 10.17 Options forfeited (1 ) 4.97 12.32 Options expired (15 ) 4.76 12.02 Options outstanding at December 31, 2017 3,311 $ 3.95 $ 10.41 As of December 31, 2019 , there were approximately 1.3 million fully vested and exercisable options. There were 1.1 million exercises during the year with an aggregate intrinsic value of $19.4 million . The weighted average exercise price for the fully vested and exercisable options was $11.22 . The remaining weighted average contractual life of fully vested and exercisable options as of December 31, 2019 was 4.79 years. The aggregate grant date intrinsic value of fully vested and exercisable options was $29.0 million as of December 31, 2019 . As of December 31, 2019 , there was $1.1 million of total unrecognized compensation cost related to non-vested stock options. The weighted-average period over which total remaining compensation costs related to non-vested stock options will be recognized is 1.31 years. The estimated grant date fair values of the stock options granted during the years ended December 31, 2019 , 2018 , and 2017 were calculated using the Black-Scholes valuation model based on the following assumptions. For the years ended December 31, 2019 2018 2017 Expected life 6 years 6 years 6 years Risk free interest rate 2.57% 2.66-2.89% 2.04-2.08% Dividend yield — % — % — % Expected stock price volatility 36.8 % 30.1-30.6% 30.5-32.7% Expected life - is the period of time over which the options granted are expected to remain outstanding giving consideration to vesting schedules, historical exercise and forfeiture patterns. We use the simplified method outlined in SEC Staff Accounting Bulletin No. 107 to estimate expected life for options granted during the period as sufficient historical exercise data is not available and the options meet the requirements set out in the Bulletin. Options granted have a maximum term of 10 years. Risk-free interest rate - is the U.S. Treasury rate on the date of the grant having a term approximating the expected life of the option. Dividend yield - is calculated by dividing the expected annual dividend by our stock price at the valuation date. Expected price volatility - is a measure of the amount by which a price has fluctuated or is expected to fluctuate. A summary of RSU activity during the years ended December 31, 2019, 2018 and 2017 is as follows: For the year ended December 31, 2019 Shares Weighted Average Grant Date Fair Value per Share (Shares in Thousands) Non-vested restricted stock units at December 31, 2018 1,753 $ 12.06 Restricted stock units granted 470 24.42 Restricted stock units vested (970 ) 9.71 Restricted stock units forfeited (51 ) 15.06 Non-vested restricted stock units at December 31, 2019 1,202 $ 18.67 For the year ended December 31, 2018 Shares Weighted Average Grant Date Fair Value per Share (Shares in Thousands) Non-vested restricted stock units at December 31, 2017 2,065 $ 8.15 Restricted stock units granted 701 17.22 Restricted stock units vested (913 ) 7.42 Restricted stock units forfeited (100 ) 9.89 Non-vested restricted stock units at December 31, 2018 1,753 $ 12.06 For the year ended December 31, 2017 Shares Weighted Average Grant Date Fair Value per Share (Shares in Thousands) Non-vested restricted stock units at December 31, 2016 2,538 $ 6.01 Restricted stock units granted 988 11.22 Restricted stock units vested (1,367 ) 6.67 Restricted stock units forfeited (94 ) 8.96 Non-vested restricted stock units at December 31, 2017 2,065 $ 8.15 At December 31, 2019 , we had 1.2 million shares of granted and non-vested RSUs, consisting of 1.0 million shares that are subject to service condition vesting requirements and 0.2 million shares that are subject to performance and service condition vesting requirements. The total fair value of RSUs vested during the year ended December 31, 2019 was $9.4 million . The remaining weighted average contractual life of non-vested RSUs was 1.37 years. As of December 31, 2019 , there was $7.2 million of total unrecognized compensation costs related to non-vested RSUs, compared to $7.8 million as of December 31, 2018 . The weighted-average period over which total remaining compensation costs related to non-vested RSUs will be recognized is 1.40 years. Non-vested RSUs subject to service condition vesting requirements vest over a service period ranging from one to five years . Non-vested RSUs subject to performance and service condition vesting requirements are scheduled to vest in 2020, with the number of shares eligible to vest based on the achievement of a return on equity goal. The fair value of non-vested RSUs is measured as the closing price of our common stock on the date of grant less the present value of anticipated dividends to be paid during the service period. 401(k) Savings Plan We offer our employees a 401(k) Savings Plan (401(k) Plan) that qualifies as a deferred salary arrangement under Section 401(k) of the Internal Revenue Code (IRC). Under the 401(k) Plan, we match up to 100% of eligible employees' pre-tax contributions up to 5% of eligible compensation. During the years ended December 31, 2019 , 2018 and 2017 , we incurred approximately $2.5 million , $1.6 million and $1.5 million of expense related to our matching 401(k) Plan contributions, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes We are a U.S. taxpayer and are subject to a statutory U.S. federal corporate income tax rate of 21%. NMIH files a consolidated U.S. federal and various state income tax returns on behalf of itself and its subsidiaries. Prior to the enactment of the Tax Cuts and Jobs Act (TCJA) on December 22, 2017, we were subject to a statutory U.S. federal corporate income tax rate of 35% for all prior years through December 31, 2017. Total income tax expense consists of the following components: For the year ended December 31, 2019 2018 2017 (In Thousands) Current $ (386 ) $ 1,677 $ 778 Deferred 45,082 26,357 29,964 Total income tax expense $ 44,696 $ 28,034 $ 30,742 For the year ended December 31, 2019 , we had income tax expense of $44.7 million , including amounts related to a current state income tax benefit and changes to our federal and state net deferred tax liability. For the year ended December 31, 2018 , we had income tax expense of $28.0 million , including amounts related to federal and state income taxes and changes to our net deferred tax liability. For the year ended December 31, 2017 , we had income tax expense of $30.7 million , including a one-time non-cash charge of $13.6 million primarily due to the re-measurement of our deferred tax assets and liabilities in connection with the enactment of the TCJA on December 22, 2017. The following table presents a reconciliation between the federal statutory income tax rate and our effective income tax rate: For the year ended December 31, 2019 2018 2017 Federal statutory income tax rate 21.0 % 21.0 % 35.0 % State provision 0.5 0.7 0.6 Share-based and other compensation (1.7 ) (1.4 ) (4.7 ) Warrant gain/loss 0.9 0.2 1.8 Re-measurement from change in federal statutory rate — — 25.7 Other (1) (0.1 ) 0.1 (0.2 ) Effective income tax rate 20.6 % 20.6 % 58.2 % (1) Prior periods have been reclassified for consistency and presentation purposes. The components of our net deferred tax asset are summarized as follows: As of December 31, 2019 2018 Deferred tax asset (In Thousands) Net operating loss carry forwards $ 9,244 $ 6,896 Share-based compensation 5,959 6,791 Unearned premium reserve 5,213 5,568 Accrued expenses 4,539 5,495 Capitalized start-up costs 634 727 Deferred ceding commissions 566 821 Unrealized loss on investments — 2,923 Other 772 364 Total gross deferred tax asset 26,927 29,585 Less: valuation allowance (7,857 ) (8,136 ) Total deferred tax asset 19,070 21,449 Deferred tax liability Contingency reserve (47,730 ) (8,149 ) Deferred acquisition costs (12,902 ) (10,145 ) Unrealized gain on investments (7,634 ) — Capitalized software (5,107 ) (4,757 ) Intangible assets (111 ) (82 ) Other (1,946 ) (1,056 ) Total deferred tax liability (75,430 ) (24,189 ) Net deferred income tax (liability) $ (56,360 ) $ (2,740 ) As a mortgage guaranty insurance company, we are eligible to claim a tax deduction for our statutory contingency reserve balance, subject to certain limitations outlined under IRC Section 832(e), to the extent we acquire tax and loss bonds in an amount equal to the tax benefit derived from the claimed deduction, which is our intent. As a result, we had no current federal income tax provision for the year ended December 31, 2019. During the year ended December 31, 2019 , we had net purchases of $7.6 million of tax and loss bonds, and as of December 31, 2019 , we held $7.6 million of tax and loss bonds in "Other assets" in our condensed consolidated balance sheet. In February 2018, the FASB issued ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income (Topic 220). This update permits the reclassification of the disproportionate income tax effects, commonly referred to as "stranded tax," that result from the TCJA on items within AOCI to retained earnings. We adopted this update effective January 1, 2018, resulting in a $0.3 million reduction to retained earnings as of January 1, 2018. The remaining $4.2 million of stranded tax that remains in AOCI relates to our available-for-sale fixed income holdings. At December 31, 2019 , we had a federal net operating loss carryforward of $2.3 million which expires in varying amounts in 2030 and 2031, and state net operating loss carryforward of $126.8 million which expire in varying amounts from 2031 to 2039. Section 382 of the IRC imposes annual limitations on a corporation's ability to utilize its net operating loss carryforwards if it experiences an "ownership change." As a result of the acquisition of our insurance subsidiaries in 2012, $7.3 million of federal net operating losses were subject to annual limitations of $0.8 million through 2016, and $0.3 million , thereafter, through 2028. Our federal net operating loss carryforward arises from this limitation and the constraint on our ability to utilize the net operating loss carryforward in full during the current period. At December 31, 2019 and 2018 , we recorded valuation allowances of $7.9 million and $8.1 million , respectively against state net deferred tax assets that may not be realized in future periods. The valuation allowances for both years primarily relate to state net operating losses generated by NMIH, as NMIH operates at a loss and currently only generates revenue from its investment portfolio. As of December 31, 2019 and 2018 , we had no reserves for unrecognized tax benefits, and had taken no material uncertain tax positions that would have required recognition and measurement. We file income tax returns with the U.S. federal government and various state jurisdictions that are subject to potential examination by tax authorities. We are not currently under examination by federal or state jurisdictions. Our U.S. federal income tax returns for 2016 and subsequent years and state income tax returns for 2015 and subsequent years remain open by statute.

Software and Equipment

Software and Equipment	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Software and Equipment	Software and Equipment Software and equipment consist largely of capitalized software developed to support our mortgage insurance operations. Software and equipment, net of accumulated amortization and depreciation, as of December 31, 2019 and 2018 , consists of the following: December 31, 2019 December 31, 2018 (In Thousands) Software $ 46,522 $ 38,450 Equipment 8,992 7,035 Leasehold improvements 3,442 3,491 Subtotal 58,956 48,976 Accumulated amortization and depreciation (32,860 ) (24,211 ) Software and equipment, net $ 26,096 $ 24,765 Capitalized costs for software, equipment, and leasehold improvements during the year ended December 31, 2019 , 2018 and 2017 , were $10.6 million , $9.8 million , and $9.1 million , respectively. Amortization and depreciation expense for software, equipment, and leasehold improvements for the years ended December 31, 2019 , 2018 , and 2017 were $9.3 million , $7.8 million , and $6.7 million , respectively.

Intangible Assets and Goodwill

Intangible Assets and Goodwill	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets and Goodwill	Intangible Assets and Goodwill Intangible assets and goodwill consist of identifiable intangible assets and goodwill purchased in connection with the acquisition of our insurance subsidiaries. Intangible assets and goodwill as of both December 31, 2019 and 2018 were as follows: (In Thousands) Expected Lives Goodwill $ 3,244 Indefinite State licenses 260 Indefinite GSE applications 130 Indefinite Total intangible assets and goodwill $ 3,634 We test goodwill and intangible assets for impairment in the third and fourth quarter, respectively, of every year, or more frequently if we believe indicators of impairment exist. No impairments of indefinite-lived intangibles or goodwill were identified during the years ended December 31, 2019 , 2018 and 2017 .

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies PMIERs As an approved insurer , NMIC is subject to ongoing compliance with the PMIERs established by each of the GSEs ( italicized terms have the same meaning that such terms have in the PMIERs, as described below). The PMIERs establish operational, business, remedial and financial requirements applicable to approved insurers . The PMIERs financial requirements prescribe a risk-based methodology whereby the amount of assets required to be held against each insured loan is determined based on certain loan-level risk characteristics, such as FICO, vintage (year of origination), performing vs. non-performing ( i.e. , current vs. delinquent), LTV and other risk features. In general, higher quality loans carry lower charges. Under the PMIERs, approved insurers must maintain available assets that equal or exceed minimum required assets , which is an amount equal to the greater of (i) $400 million or (ii) a total risk-based required asset amount . The risk-based required asset amount is a function of the risk profile of an approved insurer's net RIF, assessed on a loan-by-loan basis and considered against certain risk-based factors derived from tables set out in the PMIERs to gross RIF, which is then adjusted on an aggregate basis for reinsurance transactions approved by the GSEs, such as with respect to our ILN Transactions and QSR Transactions. The aggregate gross risk-based required asset amount for performing, primary insurance is subject to a floor of 5.6% of performing, primary adjusted RIF , and the risk-based required asset amount for pool insurance considers both factors in the PMIERs tables and the net remaining stop loss for each pool insurance policy. By April 15th of each year, NMIC must certify it met all PMIERs requirements as of December 31st of the prior year. We certified to the GSEs by April 15, 2019, that NMIC was in full compliance with the PMIERs as of December 31, 2018. NMIC also has an ongoing obligation to immediately notify the GSEs in writing upon discovery of a failure to meet one or more of the PMIERs requirements. We continuously monitor NMIC's compliance with the PMIERs. Leases We have two operating lease agreements related to our corporate headquarters and a data center facility for which we recognized operating ROU assets and lease liabilities of $6.4 million and $7.4 million in "Other assets" and "Other liabilities," respectively, on our condensed consolidated balance sheet as of December 31, 2019 . As of December 31, 2019 , we did not have any finance leases. We recognize ROU assets and lease liabilities in connection with the adoption of ASU 2016-02, Leases (Topic 842). ROU assets and lease liabilities are established based on the estimated present value of lease payments over the relevant lease term. We estimate a discount rate for each lease based on our estimated incremental borrowing rate at the commencement date of the relevant lease. ROU assets obtained in exchange for new operating lease liabilities for the year ended December 31, 2019 were $8.1 million . The following table provides a summary of our ROU asset and lease liability assumptions as of December 31, 2019 : Weighted-average remaining lease term 3.2 years Weighted-average discount rate 6.21 % Cash paid on our operating lease liabilities for the year ended December 31, 2019 was $2.5 million . Lease expenses recognized on our operating lease liabilities for the year ended December 31, 2019 were $2.2 million . Future payments due under our existing operating leases as of December 31, 2019 are as follows: Years ending December 31, (In Thousands) 2020 $ 2,537 2021 2,609 2022 2,574 2023 462 Total undiscounted lease payments 8,182 Less effects of discounting (780 ) Present value of lease payments $ 7,402 Lease expense is recorded in underwriting and operating expenses on the consolidated statements of operations. Our existing operating leases have original terms that range from three to five years . The lease for our corporate headquarters includes an option to renew for an additional five years at prevailing market rates at time of renewal. We have not included this renewal option in our calculation of minimum lease payments as it is not reasonably certain to be exercised. As of December 31, 2018, the future minimum lease payments as accounted for prior to our adoption of ASU 2016-02, Leases (Topic 842) were as follows: Years ending December 31, (In Thousands) 2019 $ 2,346 2020 2,417 2021 2,489 2022 2,564 2023 463 Totals $ 10,279 Lease expense for our corporate headquarters was $2.1 million and $1.5 million

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Common Stock	Common Stock As of December 31, 2019, we had 68.4 million outstanding shares of Class A common stock. Holders of our common stock have no preemptive or conversion rights or other subscription rights, and there are no redemption or sinking fund provisions applicable to the common stock. Each holder of our common stock is entitled to one vote for each share on all matters to be voted upon by the stockholders, and there are no cumulative voting rights. Holders of common shares are entitled to receive dividends ratably if any are declared. In March 2018, we completed the sale of 3.7 million shares of common stock and granted the underwriters on the transaction a 15% overallotment option to purchase additional shares. The overallotment option was exercised in full, resulting in a total of 4.3 million shares of common stock issued. The common stock offering generated total proceeds of approximately $79.2 million , net of underwriting discounts, commissions and other direct offering expenses.

Regulatory Information

Regulatory Information	12 Months Ended
	Dec. 31, 2019
Insurance [Abstract]
Regulatory Information	Regulatory Information Statutory Requirements Our insurance subsidiaries, NMIC and Re One, file financial statements in conformity with statutory accounting principles (SAP) prescribed or permitted by the Wisconsin OCI, NMIC's principal regulator. Prescribed SAP includes state laws, regulations and general administrative rules, as well as a variety of publications of the National Association of Insurance Commissioners (NAIC). The Wisconsin OCI recognizes only statutory accounting practices prescribed or permitted by the state of Wisconsin for determining and reporting the financial condition and results of operations of an insurance company and for determining its solvency under Wisconsin insurance laws. NMIC and Re One's combined statutory net gain (loss), statutory surplus, contingency reserve and risk-to-capital (RTC) ratios as of and for the years ended December 31, 2019 , 2018 and 2017 were as follows: As of and for the year ended December 31, 2019 2018 2017 (In Thousands) Statutory net gain (loss) $ 15,233 $ (19,784 ) $ (35,946 ) Statutory surplus 449,602 430,785 371,084 Contingency reserve 531,825 332,702 186,641 Risk-to-capital 15.8:1 13.1:1 13.2:1 Under applicable law in Wisconsin and 15 other states, mortgage insurers must maintain minimum amounts of statutory capital relative to RIF to continue to write new business. While formulations of minimum statutory capital may vary in each state, the most common measure allows for a maximum permitted RTC ratio of 25:1 . Wisconsin and certain other states, including California and Illinois, apply a substantially similar requirement referred to as minimum policyholders' position. The NAIC's Mortgage Guaranty Insurance Working Group (the Working Group) was formed to discuss, develop and recommend changes to the solvency and market practices regulation of mortgage insurers, including changes to the Mortgage Guaranty Insurance Model Act (Model Act). Proposed amendments to the Model Act include, among other changes, adoption of a risk-based capital model. Following adoption by the NAIC, some or all of the 16 states that currently have minimum statutory capital requirements, and potentially others that do not, are expected to enact a portion or all of the revised Model Act, including the loan-level capital model. As of December 31, 2019 , NMIC's performing primary RIF, net of reinsurance, was approximately $ 15.4 billion and its RTC ratio was 16.3:1 , significantly below applicable limits. As of December 31, 2018 , NMIC's performing primary RIF, net of reinsurance, was approximately $ 10.0 billion and its RTC ratio was 13.7:1 . Reinsurance Prior to January 10, 2019, Ohio regulation limited the amount of risk a mortgage insurer was permitted to retain on a single loan to 25% of the borrower's indebtedness (after giving effect to third-party reinsurance) and, as a result, the portion of such insurance in excess of 25% was required to be reinsured. Ohio repealed this requirement for future periods beginning January 10, 2019. Several other states previously imposed similar coverage restrictions and repealed these measures prior to 2018. To comply with these previous state coverage limits, NMIC and Re One have reinsurance agreements in place under which Re One provides reinsurance to NMIC on certain insured loans with coverage levels in excess of 25% , after giving effect to third-party reinsurance. Dividend Restrictions NMIH is not subject to any limitations on its ability to pay dividends except those generally applicable to corporations that are incorporated in Delaware. Delaware corporate law provides that dividends are only payable out of a corporation's capital surplus or, subject to certain limitations, recent net profits. As of December 31, 2019 , NMIH's shareholders' equity was approximately $ 930.4 million. NMIC and Re One are subject to certain capital and dividend rules and regulations prescribed by jurisdictions in which they are authorized to operate and the GSEs. Under Wisconsin law, NMIC and Re One may pay dividends up to specified levels ( i.e. , "ordinary" dividends) with 30 days' prior notice to the Wisconsin OCI. Dividends in larger amounts ( i.e. ,"extraordinary" dividends), are subject to the Wisconsin OCI's prior approval. Under Wisconsin law, an extraordinary dividend is defined as any payment or distribution that together with other dividends and distributions made within the preceding 12 months exceeds the lesser of (i) 10% of the insurer's statutory policyholders' surplus as of the preceding December 31 or (ii) adjusted statutory net income for the 12-month period ending the preceding December 31. NMIC and Re One have never paid dividends to NMIH. NMIC and Re One have the capacity to pay aggregate ordinary dividends of $16.1 million to NMIH during the 12-month period ending December 31, 2020. As an approved insurer under PMIERs, NMIC would be subject to prior GSE approval of its ability to pay dividends to NMIH if it failed to meet the financial requirements prescribed by PMIERs.

Quarterly Financial Data (Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data (Unaudited)	Quarterly Financial Data (Unaudited) 2019 Quarters 2019 First Second Third Fourth Year (In Thousands, except per share data) Net premiums earned $ 73,868 $ 83,249 $ 92,381 $ 95,517 $ 345,015 Net investment income 7,383 7,629 7,882 7,962 30,856 Net realized investment (losses) gains (187 ) (113 ) 81 264 45 Other revenues 42 415 1,244 1,154 2,855 Insurance claims and claim expenses 2,743 2,923 2,572 4,269 12,507 Underwriting and operating expenses (1) 30,800 32,190 32,335 31,296 126,621 Service expenses (1) 49 353 909 937 2,248 Interest expense 3,061 3,071 2,979 2,974 12,085 Loss (gain) from change in fair value of warrant liability 5,479 1,685 (1,139 ) 2,632 8,657 Pre-tax income 38,974 50,958 63,932 62,789 216,653 Income tax expense 6,075 11,858 14,169 12,594 44,696 Net income $ 32,899 $ 39,100 $ 49,763 $ 50,195 $ 171,957 Income per share: (2) Basic earnings per share $ 0.49 $ 0.58 $ 0.73 $ 0.74 $ 2.54 Diluted earnings per share $ 0.48 $ 0.56 $ 0.69 $ 0.71 $ 2.47 Weighted average common shares outstanding - basic 66,692 67,590 67,849 68,140 67,573 Weighted average common shares outstanding - diluted 68,996 69,590 70,137 70,276 69,721 (1) Certain "Underwriting and operating expenses" have been reclassified as "Service expenses" in prior periods. (2) Due to the use of weighted average shares outstanding when calculating EPS , the sum of quarterly per share data may not equal the per share data for the year. 2018 Quarters 2018 First Second Third Fourth Year (In Thousands, except per share data) Net premiums earned $ 54,914 $ 61,615 $ 65,407 $ 69,261 $ 251,197 Net investment income 4,574 5,735 6,277 6,952 23,538 Net realized investment gains (losses) — 59 (8 ) 6 57 Other revenues 64 44 85 40 233 Insurance claims and claim expenses 1,569 643 1,099 2,141 5,452 Underwriting and operating expenses (1) 28,346 28,958 30,323 29,339 116,966 Service expenses (1) 107 62 56 45 270 Interest expense 3,419 5,560 2,972 3,028 14,979 (Gain) loss from change in fair value of warrant liability (420 ) (109 ) 5,464 (3,538 ) 1,397 Pre-tax income 26,531 32,339 31,847 45,244 135,961 Income tax expense 4,176 7,098 7,036 9,724 28,034 Net income $ 22,355 $ 25,241 $ 24,811 $ 35,520 $ 107,927 Income per share: (2) Basic earnings per share $ 0.36 $ 0.38 $ 0.38 $ 0.54 $ 1.66 Diluted earnings per share $ 0.34 $ 0.37 $ 0.36 $ 0.46 $ 1.60 Weighted average common shares outstanding - basic 62,099 65,664 65,948 66,308 65,019 Weighted average common shares outstanding - diluted 65,697 68,616 68,844 69,013 67,652 (1) Certain "Underwriting and operating expenses" have been reclassified as "Service expenses" in prior periods. (2) Due to the use of weighted average shares outstanding when calculating EPS, the sum of quarterly per share data may not equal the per share data for the year.

SCHEDULE I - SUMMARY OF INVESTM

SCHEDULE I - SUMMARY OF INVESTMENTS - OTHER THAN INVESTMENTS IN RELATED PARTIES	12 Months Ended
	Dec. 31, 2019
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Abstract]
Summary of Investments - Other than Investments in Related Parties	December 31, 2019 Amortized Cost Fair Value Amount Reflected on Balance Sheet (In Thousands) U.S. Treasury securities and obligations of U.S. government agencies $ 48,203 $ 48,929 $ 48,929 Municipal debt securities 189,530 190,216 190,216 Corporate debt securities 661,719 684,881 684,881 Asset-backed securities 170,153 172,642 172,642 Total bonds 1,069,605 1,096,668 1,096,668 Short-term investments 44,174 44,272 44,272 Total investments $ 1,113,779 $ 1,140,940 $ 1,140,940

SCHEDULE II - FINANCIAL INFORMA

SCHEDULE II - FINANCIAL INFORMATION OF REGISTRANT- PARENT COMPANY ONLY	12 Months Ended
	Dec. 31, 2019
Condensed Financial Information Disclosure [Abstract]
Financial Information of Registrant Parent Company Only	December 31, 2019 December 31, 2018 (In Thousands, except for share data) Assets Fixed maturities, available-for-sale, at fair value $ 41,220 $ 51,957 Cash and cash equivalents 13,431 12,345 Investment in subsidiaries, at equity in net assets 1,025,286 766,193 Accrued investment income 219 216 Prepaid expenses 3,332 3,118 Due from affiliates, net 62,241 41,340 Software and equipment, net 26,096 24,766 Other assets 7,188 1,664 Total assets $ 1,179,013 $ 901,599 Liabilities Term loan $ 145,764 $ 146,757 Accounts payable and accrued expenses 24,871 27,237 Warrant liability, at fair value 7,641 7,296 Deferred tax liability, net 62,921 18,809 Other liabilities 7,396 — Total liabilities 248,593 200,099 Shareholders' equity Common stock - class A shares, $0.01 par value; 68,358,074 and 66,318,849 shares issued and outstanding as of December 31, 2019 and December 31, 2018, respectively (250,000,000 shares authorized) 684 663 Additional paid-in capital 707,003 682,181 Accumulated other comprehensive income (loss), net of tax 17,288 (14,832 ) Retained earnings 205,445 33,488 Total shareholders' equity 930,420 701,500 Total liabilities and shareholders' equity $ 1,179,013 $ 901,599 For the year ended December 31, 2019 2018 2017 (In Thousands) Revenues Net investment income $ 1,124 $ 1,145 $ 691 Net realized investment gains 1 5 1 Total revenues 1,125 1,150 692 Expenses Other operating expenses 11,714 21,095 16,374 Interest expense — 2,227 — Loss from change in fair value of warrant liability 8,657 1,397 4,105 Total expenses 20,371 24,719 20,479 Equity in net income of subsidiaries 226,480 134,127 67,146 Income before income taxes 207,234 110,558 47,359 Income tax expense 35,277 2,631 25,309 Net income $ 171,957 $ 107,927 $ 22,050 Other comprehensive income (loss), net of tax: Unrealized gains (losses) in accumulated other comprehensive loss, net of tax expense (benefit) of $82, ($34), and ($49) for each of the years in the three-year period ended December 31, 2019, respectively 308 (128 ) (90 ) Reclassification adjustment for losses (gains) included in net loss, net of tax (benefit) expense of $0, ($1) and $0 for each of the years in the three-year period ended December 31, 2019, respectively — 2 (1 ) Equity in other comprehensive income (loss) of subsidiaries 31,812 (12,129 ) 2,519 Other comprehensive income (loss), net of tax 32,120 (12,255 ) 2,428 Comprehensive income $ 204,077 $ 95,672 $ 24,478 For the year ended December 31, 2019 2018 2017 Cash flows from operating activities (In Thousands) Net income $ 171,957 $ 107,927 $ 22,050 Adjustments to reconcile net income to net cash (used in) provided by operating activities: Loss from change in fair value of warrant liability 8,657 1,397 4,105 Net realized investment gains (1 ) (5 ) (1 ) Depreciation and amortization 286 274 233 Amortization of debt discount and debt issuance costs 1,011 3,390 1,474 Deferred income taxes 44,030 25,163 30,876 Share-based compensation expense 13,031 12,557 9,484 Changes in operating assets and liabilities: Equity in net income of subsidiaries (1) (226,480 ) (133,837 ) (67,239 ) Accrued investment income (3 ) (14 ) (52 ) Receivable from affiliates (20,902 ) (18,932 ) (13,103 ) Prepaid expenses (409 ) (1,010 ) (116 ) Other assets 165 1,258 (1,523 ) Accounts payable and accrued expenses (1,640 ) 5,393 (3,463 ) Net cash (used in) provided by operating activities (10,298 ) 3,561 (17,275 ) Cash flows from investing activities Capitalization of subsidiaries (800 ) (70,500 ) (300 ) Purchase of short-term investments (104,192 ) (134,376 ) (98,255 ) Purchase of fixed-maturity investments, available-for-sale (2,186 ) (12,906 ) (19,884 ) Proceeds from maturity of short-term investments 111,539 122,612 114,170 Proceeds from redemptions, maturities and sale of fixed-maturity investments, available-for-sale 5,877 22,954 11,451 Software and equipment (854 ) (415 ) (1,996 ) Net cash provided by (used in) investing activities 9,384 (72,631 ) 5,186 Cash flows from financing activities Proceeds from issuance of common stock related to public offering, net of issuance costs — 79,165 — Proceeds from issuance of common stock related to employee equity plans 21,748 12,857 7,103 Proceeds from issuance of common stock related to warrant exercises — 321 183 Taxes paid related to net share settlement of equity awards (18,248 ) (9,722 ) (8,582 ) Proceeds from term loan, net — 149,250 — Repayments of term loan (1,500 ) (147,375 ) (1,500 ) Payments of debt issuance/modification costs — (3,609 ) (445 ) Net cash provided by (used in) financing activities 2,000 80,887 (3,241 ) Net increase (decrease) in cash, cash equivalents and restricted cash 1,086 11,817 (15,330 ) Cash, cash equivalents and restricted cash, beginning of period 12,345 528 15,858 Cash, cash equivalents and restricted cash, end of period $ 13,431 $ 12,345 $ 528 (1) Amount in 2018 includes $0.3 million reduction to retained earnings as of January 1, 2018 as a result of the adoption of ASU 2018-02. For more information related to this adjustment, See Item 8, " Financial Statements and Supplementary Data - Notes to Consolidated Financial Statements - Note 11, Income Taxes ." Note A The NMI Holdings, Inc. (Parent Company) financial statements represent the stand-alone financial statements of the Parent Company. 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. Refer to the Parent Company's consolidated financial statements for additional information. Note B Our insurance subsidiaries are subject to certain capital and dividend rules and regulations prescribed by jurisdictions in which they are authorized to operate and the GSEs. Under Wisconsin law, NMIC and Re One may pay dividends up to specified levels ( i.e. , "ordinary" dividends) with 30 days' prior notice to the Wisconsin OCI. Dividends in larger amounts ( i.e. ,"extraordinary" dividends), are subject to the Wisconsin OCI's prior approval. Under Wisconsin law, an extraordinary dividend is defined as any payment or distribution that together with other dividends and distributions made within the preceding 12 months exceeds the lesser of (i) 10% of the insurer's statutory policyholders' surplus as of the preceding December 31 or (ii) adjusted statutory net income for the 12-month period ending the preceding December 31. NMIC and Re One have the capacity to pay aggregate ordinary dividends of $16.1 million to NMIH during the 12-month period ending December 31, 2020, and their remaining net assets are considered restricted. As of December 31, 2019 , the amount of restricted net assets held by our consolidated insurance subsidiaries, which represents our equity investment in those insurance subsidiaries less their aggregate dividend capacity, totaled $ 1.0 billion, compared to $ 0.8 billion as of December 31, 2018. Note C The Parent Company provides certain services to its subsidiaries. The Parent Company allocates to its subsidiaries corporate expense it incurs in the capacity of supporting those subsidiaries, based on either an allocated percentage of time spent or internally allocated capital. Total operating expenses allocated to subsidiaries for each of the years in the three year period ended December 31, 2019 were $117.1 million , $111.6 million and $101.0 million , respectively. Amounts charged to the subsidiaries for operating expenses are based on actual cost, without any mark-up. The Parent Company considers these charges fair and reasonable. The subsidiaries reimburse the Parent Company for these costs in a timely manner, which has the impact of improving the cash flows of the Parent Company.

SCHEDULE IV - FINANCIAL INFORMA

SCHEDULE IV - FINANCIAL INFORMATION OF REGISTRANT REINSURANCE	12 Months Ended
	Dec. 31, 2019
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Abstract]
Financial Information of Registrant Reinsurance	Gross Amount Ceded to Other Companies Assumed from Other Companies Net Amount Percentage of Amount Assumed to Net For the years ended December 31, (In thousands) 2019 $ 398,303 $ 53,288 $ — $ 345,015 — % 2018 292,064 40,867 — 251,197 — % 2017 192,326 26,586 — 165,740 — % 2016 115,830 5,349 — 110,481 — %

Summary of Accounting Policies

Summary of Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements include the results of NMIH and its wholly-owned subsidiaries. All inter-company transactions have been eliminated. These financial statements have been prepared in accordance with accounting principles generally accepted in the U.S. (GAAP) and our accounts are maintained in US dollars. The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect reported amounts of assets and liabilities, as well as disclosure of contingent assets and liabilities as of the balance sheet date. Estimates also affect the reported amounts of income and expenses for the reporting period. Actual results could differ from those estimates. Certain reclassifications to previously reported financial information have been made to conform to our current period presentation.
Use of Estimates	Use of Estimates We use accounting principles and methods that conform to GAAP. We are required to apply significant judgment and make material estimates in the preparation of our financial statements and with regard to various accounting, reporting and disclosure matters. Assumptions and estimates are required to apply these principles where actual measurement is not possible or practical.
Insurance Premium Revenue Recognition	Insurance Premium Revenue Recognition Premiums for primary mortgage insurance policies may be paid in a single payment at origination (single premium), on a monthly installment basis (monthly premium) or on an annual installment basis (annual premium), with such election and payment type fixed at policy inception. Premiums written at origination for single premium policies are initially deferred as unearned premiums and amortized into earnings over the estimated policy life, in accordance with the anticipated expiration of risk. Monthly premiums are recognized as revenue in the month billed and when the coverage is effective. Annual premiums are initially deferred and earned on a straight-line basis over the year of coverage. Upon cancellation of a policy, all remaining non-refundable deferred and unearned premium is immediately earned, and any refundable deferred premium is returned to the policyholder and recorded as a reduction to written premium and unearned premium reserve in the period paid. Premiums written on pool transactions are earned over the period that coverage is provided.
Reserve for Insurance Claims and Claims Expenses	Reserves for Insurance Claims and Claim Expenses We establish reserves for claims based on our best estimate of ultimate claim costs for defaulted loans using the general principles contained in ASC 944, Financial Services - Insurance (ASC 944). We establish case reserves when we are notified that a loan has been in default for at least 60 days ( i.e ., a default) and "IBNR" reserves based on an estimate of defaults which have been incurred but have not yet been reported to us by loan servicers. We also establish reserves for claim expenses, which represent the estimated cost of the claim administration process, including legal, other third-party fees, and other general expenses of administering the claim settlement process. Claim expense reserves are either allocated ( i.e. , associated with a specific claim) or unallocated ( i.e. , not associated with a specific claim). The establishment of claims and claim expense reserves is subject to inherent uncertainty and requires significant judgment by management. Reserves are established by estimating the number of loans in default that will result in a claim payment, which is referred to as claim frequency, and the amount of the claim payment expected to be paid on each such loan in default, which is referred to as claim severity. Claim frequency and severity estimates are established based on historical observed experience regarding certain loan factors, such as age of the default, size of the loan and loan-to-value (LTV) ratios, and are strongly influenced by prevailing economic conditions, such as mortgage rates, trends in unemployment and house price appreciation. We conduct an annual actuarial review to evaluate and, if necessary, update these assumptions.
Investments	Investments We have designated our investment portfolio as available-for-sale and report it at fair value. The related unrealized gains and losses, after considering the related tax expense or benefit, are recognized as a component of accumulated other comprehensive income (AOCI) (loss) in shareholders' equity. Net realized investment gains and losses are reported in income based on specific identification of securities sold or other-than-temporarily impaired, and are reclassified out of AOCI (loss). We measure fair value and classify invested assets in a hierarchy for disclosure purposes consisting of three "levels" based on the observability of inputs available in the marketplace used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). See Note 4, " Fair Value of Financial Instruments " for further discussion. Purchases and sales of investments are recorded on a trade date basis. Net investment income is recognized when earned, and includes interest and dividend income together with amortization of market premiums and discounts using the effective yield method, and is net of investment management fees and other investment related expenses. For asset-backed securities and any other holdings for which there is a prepayment risk, prepayment assumptions are evaluated and revised as necessary. Any adjustments required due to changes in effective yields and maturities are recognized on a prospective basis through yield adjustments. We evaluate our investments each quarter to determine whether declines in fair value below amortized cost are considered other-than-temporary in accordance with applicable guidance. Under the current guidance, a debt security impairment is deemed other-than-temporary if (i) we either intend to sell the security or it is more likely than not that we will be required to sell the security before recovery or (ii) we do not expect to collect cash flows sufficient to recover the amortized cost basis of the security. In evaluating whether a decline in fair value is other-than-temporary, we consider several factors including, but not limited to: • our intent to sell the security or whether it is more likely than not that we will be required to sell the security before recovery; • the severity and duration of the decline in fair value; • the financial condition of the issuer; • the failure of the issuer to make scheduled interest or principal payments; • recent credit downgrades of the applicable security or the issuer; and • adverse conditions specifically related to the security, an industry, or a geographic area. Based on this evaluation, we record OTTI adjustments on securities with declines in fair value below their amortized cost, if it is more likely than not that we will sell the securities prior to recovery of their amortized cost or if the present value of the discounted cash flows we expect to collect on the securities through recovery under a "most likely" scenario is less than their amortized cost. If our intent is to sell securities and their fair value is below amortized cost, the securities are classified as other-than-temporarily impaired and the full amount of the impairment is recognized as a loss in earnings. Otherwise, losses on other-than-temporarily impaired securities are bifurcated between credit-related losses and losses related to other factors ( e.g. , interest rate fluctuations), with credit-related losses recognized in earnings and losses related to other factors recognized in AOCI (loss), net of taxes. We consider items such as commercial paper with original maturities of 90 days or less to be short-term investments.
Deferred Policy Acquisition Costs (DAC)	Deferred Policy Acquisition Costs (DAC)
Premium Deficiency Reserves	Premium Deficiency Reserves
Reinsurance	Reinsurance We account for premiums, claims and claim expenses that are ceded to reinsurers on a consistent basis with that which we use to account for the original policies we issue and pursuant to the terms of our reinsurance contracts. We account for premiums ceded or otherwise paid to reinsurers as a reduction to premium revenue. NMIC entered into quota share reinsurance treaties effective September 1, 2016 (the 2016 QSR Transaction) and January 1, 2018 (the 2018 QSR Transaction), which we refer to collectively as the QSR Transactions. We earn profit and ceding commissions in connection with the QSR Transactions (see Note 6, " Reinsurance "). Profit commissions represent a percentage of the profits recognized by reinsurers that are returned to us, based on the level of claims and claim expenses that we cede. We recognize any profit commissions we earn as an increase to premium revenue. Ceding commissions are calculated as a percentage of ceded written premiums under the 2016 QSR Transaction and as a percentage of ceded earned premiums under the 2018 QSR Transaction, and are intended to cover our costs of acquiring and servicing direct policies. We recognize any ceding commissions we earn in a manner consistent with our recognition of earnings on the underlying insurance policies, over the terms of the policies reinsured. We account for ceding commissions earned as a reduction to underwriting and operating expenses. Under the QSR Transactions, we cede a portion of claims and claim expense reserves to our reinsurers, and account for such ceded reserves as reinsurance recoverables in "Other Assets" on the consolidated balance sheets and as reductions to claims expenses on the consolidated statements of operations. We remain directly liable for all claims payments if we are unable to collect from any reinsurer.
Income Taxes	Income Taxes We account for income taxes using the liability method in accordance with ASC Topic 740, Income Taxes . The liability method measures the expected future tax effects of temporary differences at the enacted tax rates applicable for the period in which the deferred asset or liability is expected to be realized or settled. Temporary differences are differences between the tax basis of an asset or liability and its reported amount in the consolidated financial statements that would result in future increases or decreases in taxes owed on a cash basis compared to amounts already recognized as tax expense in the consolidated statement of operations.
Warrants	Warrants We account for warrants to purchase our common shares in accordance with ASC 470-20, Debt with Conversion and Other Options and ASC 815-40 Derivatives and Hedging - Contracts in Entity's Own Equity . Our outstanding warrants may be settled through either (i) physical settlement method, or (ii) cashless exercise, where the number of shares issued upon exercise of the warrants is reduced to cover the cost of the exercise in lieu of the holder remitting a cash payment for the exercise price. The warrants expire and are not exercisable after the 10th anniversary of the date issued. The number of warrants and exercise price are subject to anti-dilution provisions whereby the number of warrants may be increased and their exercise price may be adjusted downward under certain circumstances. The anti-dilutive adjustments may be in excess of any dilution incurred by the warrant holders, and may be triggered by events that are not dilutive. As a result, the warrants are classified as a liability. We revalue the warrants at the end of each reporting period, and any change in fair value is reported in the statements of operations in the period in which the change occurred. We calculated the fair value of the warrants using a Black-Scholes option-pricing model in combination with a binomial model.
Share-Based Compensation	Share-Based Compensation We account for stock compensation in accordance with ASC 718, Compensation - Stock Compensation , which addresses accounting for share-based awards and recognition of compensation expense, measured using grant date fair value, over the requisite service or performance period of the award. Share-based compensation includes restricted stock units (RSUs) and stock option grants under our Stock Plans. We calculate the fair value of stock option grants using a Black-Scholes option pricing model, which takes into account various subjective assumptions. Key assumptions used in the model include the expected volatility of our stock price, dividend yield and the risk-free interest rate, as well as the expected option term, giving consideration to the contractual terms of any award. RSU grants may contain a service condition, or performance and service conditions. RSU grants are valued at our stock price on the date of grant less the present value of anticipated dividends. We account for stock option and RSU forfeitures as they occur.
Earnings per Share (EPS)	Earnings per Share (EPS) Basic earnings (loss) per share is based on the weighted-average number of common shares outstanding. Diluted earnings (loss) per share is based on the weighted-average number of common shares outstanding and common share equivalents that would be issuable upon the vesting of existing service based and certain performance and service based RSUs, and exercise of vested and unvested stock options and outstanding warrants.
Cash and Cash Equivalents	Cash and Cash Equivalents We consider items such as certificates of deposit and money market funds with original maturities of 90 days or less to be cash equivalents.
Software and Equipment	Software and Equipment We capitalize certain costs associated with the development of internal-use software and equipment. Software and equipment are stated at cost, less accumulated amortization and depreciation. Amortization of software and depreciation of equipment commences at the beginning of the month following our placement of the assets into use. Amortization and depreciation are calculated on a straight-line basis over the estimated useful life of the respective assets, typically from three to five years
Business Combinations, Goodwill and Intangible Assets	Business Combinations, Goodwill and Intangible Assets Goodwill represents the excess of the purchase price over the estimated fair value of net assets acquired from a business combination. In accordance with ASC 350, Intangibles - Goodwill and Other , we test goodwill for impairment during the third quarter each year, or more frequently if we believe indicators of impairment exist. We have not identified any impairments of goodwill through December 31, 2019.
Premiums Receivable	Premiums Receivable Premiums receivable consist of premiums due on our mortgage insurance policies. If a mortgage insurance premium is unpaid for more than 120 days, the receivable is written off against earned premium and the related insurance policy is canceled. Premiums receivable may be written off prior to 120 days in the ordinary course of business for reasons including, but not limited to, the modification or refinancing of underlying insured loans. We have established a reserve for premium write-offs based on historical experience; such reserve was deemed to be immaterial for the years ended December 31, 2019 and December 31, 2018.
Variable interest entities	Variable Interest Entities NMIC is a party to reinsurance agreements with three special purpose reinsurance entities - Oaktown Re Ltd., Oaktown Re II Ltd. and Oaktown Re III Ltd. - respectively dated May 2, 2017, July 25, 2018 and July 30, 2019. At inception of the respective reinsurance agreements, we determined that Oaktown Re Ltd., Oaktown Re II, Ltd. and Oaktown Re III, Ltd, were variable interest entities (VIEs), as defined under GAAP Accounting Standards Codification (ASC) 810, because they did not have sufficient equity at risk to finance their respective activities. We evaluated the VIEs at inception to determine whether NMIC was the primary beneficiary under each deal and, if so, whether we were required to consolidate the assets and liabilities of each VIE. The primary beneficiary of a VIE is an enterprise that (1) has the power to direct the activities of the VIE, which most significantly impact its economic performance and (2) has significant economic exposure to the VIE, i.e., the obligation to absorb losses or receive benefits that could potentially be significant. The determination of whether an entity is the primary beneficiary of a VIE is complex and requires management judgment regarding determinative factors, including the expected results of the VIE and how those results are absorbed by beneficial interest holders, as well as which party has the power to direct activities that most significantly impact the performance of the VIE. We concluded that we are not the primary beneficiary of each VIE and as such, we do not consolidate them in our consolidated financial statements.
Recent Accounting Pronouncements	Recent Accounting Pronouncements - Adopted In February 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2016-02, Leases (Topic 842). This update requires that businesses recognize rights and obligations associated with certain leases as assets and liabilities on the balance sheet. The standard also requires additional disclosures regarding the amount, timing, and uncertainty of cash flows arising from leases. We adopted this ASU on January 1, 2019 using the modified-retrospective method and applied it prospectively as of the effective date, without adjusting comparative periods presented as permitted by ASU 2018-11, Leases (Topic 842), Targeted Improvements . Adoption of this new standard increased our assets and liabilities by $7.6 million in connection with the recognition of right-of-use (ROU) assets and lease liabilities, primarily related to the operating lease on our corporate headquarters. Adoption of this standard did not impact our consolidated statements of operations or cash flows. See Note 14, " Commitments and Contingencies " for additional information related to our leases. In July 2017, the FASB issued ASU 2017-11, Earnings Per Share (Topic 260), Distinguishing Liabilities from Equity (Topic 480), and Derivatives and Hedging (Topic 815). This update is intended to simplify the accounting for certain equity-linked financial instruments. We adopted this ASU on January 1, 2019. Adoption of this standard had no impact on our consolidated financial statements. In June 2018, the FASB issued ASU 2018-07, Compensation-Stock Compensation (Topic 718). This update expands the scope of Topic 718 to include share-based payments made to non-employees in connection with the acquisition of goods and services. We adopted this ASU on January 1, 2019. Adoption of this standard had no impact on our financial results as we have not made any share-based grants to non-employees as defined in ASC 718-10-20. Recent Accounting Pronouncements - Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326) and subsequently issued amendments to the initial guidance: ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments, ASU 2019-05, Financial Instruments-Credit Losses: Targeted Transition Relief, and ASU 2019-11, Codification Improvements to Topic 326, Financial Instruments-Credit Losses . These updates will require companies to measure and establish reserves for lifetime expected credit losses on many financial assets held at a given reporting date. Under the guidance, the methodology for measuring lifetime credit losses will generally shift from an incurred loss model, whereby losses are only recognized once probable and estimable, to a current expected credit loss (CECL) model, whereby losses are recognized upfront based on a future economic forecast. Credit losses relating to available-for-sale fixed maturity securities will be recorded through an allowance for credit losses, rather than a write-down of the asset as is currently required, with the amount of the allowance limited to the amount by which fair value is less than amortized cost. The length of time an available-for sale fixed maturity security has been held in an unrealized loss position will no longer impact its credit loss determination. We adopted these updates on January 1, 2020. Adoption of the updated standards did not have a material impact on our consolidated financial statements, and had no impact on our accounting for insurance claims and claim expenses as these items are not in scope of the guidance. In August 2018, the FASB issued ASU 2018-12, Targeted Improvements to the Accounting for Long-Duration Contracts . This update provides guidance to the existing recognition, measurement, presentation and disclosure requirements for long-duration contracts issued by an insurance entity. The FASB subsequently issued ASU 2019-19 in November 2019 and amended the effective date for this standard. The standard will now take effect for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2021. We are currently evaluating the impact the adoption of this ASU will have, if any, on our consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820). This update modifies the fair value measurement disclosure requirements of ASC 820. We adopted this ASU on January 1, 2020 and determined it did not have a material impact on our consolidated financial statements. In August 2018, the FASB issued ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40).This update applies to cloud computing arrangements structured as service contracts, and provides companies with guidance on the criteria for capitalizing implementation, set-up and other up-front costs incurred in association with these arrangements. We adopted this ASU on January 1, 2020 and applied it on a prospective basis for eligible costs incurred after the effective date. The adoption of this ASU did not have a material impact on our consolidated financial statements. In November 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740). This update eliminates certain exceptions for recognizing deferred taxes for investments, performing intra-period allocations and calculating income taxes in interim periods. The ASU also includes guidance to reduce complexity in certain income tax areas, including recognizing deferred taxes for tax goodwill and allocating taxes to members of a consolidated group. The standard will take effect for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020. We are currently evaluating the impact the adoption of this ASU will have, if any, on our consolidated financial statements.

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Schedule of Fair Values and Gross Unrealized Gains and Losses	Fair Values and Gross Unrealized Gains and Losses on Investments Amortized Gross Unrealized Fair Gains Losses As of December 31, 2019 (In Thousands) U.S. Treasury securities and obligations of U.S. government agencies $ 48,203 $ 784 $ (58 ) $ 48,929 Municipal debt securities 189,530 1,721 (1,035 ) 190,216 Corporate debt securities 661,719 23,373 (211 ) 684,881 Asset-backed securities 170,153 2,603 (114 ) 172,642 Total bonds 1,069,605 28,481 (1,418 ) 1,096,668 Short-term investments 44,174 98 — 44,272 Total investments $ 1,113,779 $ 28,579 $ (1,418 ) $ 1,140,940 Amortized Gross Unrealized Fair Gains Losses As of December 31, 2018 (In Thousands) U.S. Treasury securities and obligations of U.S. government agencies $ 48,171 $ 35 $ (1,376 ) $ 46,830 Municipal debt securities 92,014 206 (963 ) 91,257 Corporate debt securities 554,079 847 (11,688 ) 543,238 Asset-backed securities 171,990 792 (1,457 ) 171,325 Total bonds 866,254 1,880 (15,484 ) 852,650 Short-term investments 58,733 107 — 58,840 Total investments $ 924,987 $ 1,987 $ (15,484 ) $ 911,490
Schedule of Investments by Industry Group	The following table presents a breakdown of the fair value of our corporate debt securities by issuer industry group as of December 31, 2019 and 2018 : December 31, 2019 December 31, 2018 Financial 38 % 38 % Consumer 26 27 Communications 10 12 Utilities 9 7 Industrial 8 7 Technology 7 6 Energy 2 2 Other — 1 Total 100 % 100 %
Schedule of Investments by Maturity	The amortized cost and fair values of available-for-sale securities as of December 31, 2019 and 2018, by contractual maturity, are shown below. Expected maturities will differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. Because most asset-backed securities provide for periodic payments throughout their lives, they are listed below in a separate category. As of December 31, 2019 Amortized Fair (In Thousands) Due in one year or less $ 138,776 $ 139,113 Due after one through five years 406,986 417,208 Due after five through ten years 380,737 394,180 Due after ten years 17,127 17,797 Asset-backed securities 170,153 172,642 Total investments $ 1,113,779 $ 1,140,940 As of December 31, 2018 Amortized Fair (In Thousands) Due in one year or less $ 76,087 $ 76,104 Due after one through five years 352,282 347,701 Due after five through ten years 318,728 310,633 Due after ten years 5,900 5,727 Asset-backed securities 171,990 171,325 Total investments $ 924,987 $ 911,490
Schedule of Aging Unrealized Losses	or those securities in an unrealized loss position, the length of time the securities were in such a position is as follows: Less Than 12 Months 12 Months or Greater Total # of Securities Fair Value Unrealized Losses # of Securities Fair Value Unrealized Losses # of Securities Fair Value Unrealized Losses As of December 31, 2019 (Dollars in Thousands) U.S. Treasury securities and obligations of U.S. government agencies 4 $ 12,001 $ (58 ) — $ — $ — 4 $ 12,001 $ (58 ) Municipal debt securities 26 92,844 (1,034 ) 1 999 (1 ) 27 93,843 (1,035 ) Corporate debt securities 10 30,481 (140 ) 14 23,976 (71 ) 24 54,457 (211 ) Asset-backed securities 9 19,236 (102 ) 1 2,988 (12 ) 10 22,224 (114 ) Total 49 $ 154,562 $ (1,334 ) 16 $ 27,963 $ (84 ) 65 $ 182,525 $ (1,418 ) Less Than 12 Months 12 Months or Greater Total # of Securities Fair Value Unrealized Losses # of Securities Fair Value Unrealized Losses # of Securities Fair Value Unrealized Losses As of December 31, 2018 (Dollars in Thousands) U.S. Treasury securities and obligations of U.S. government agencies — $ — $ — 19 $ 41,817 $ (1,376 ) 19 $ 41,817 $ (1,376 ) Municipal debt securities 4 7,409 (11 ) 31 58,658 (952 ) 35 66,067 (963 ) Corporate debt securities 118 226,477 (3,952 ) 126 221,675 (7,736 ) 244 448,152 (11,688 ) Asset-backed securities 25 36,017 (1,136 ) 22 33,988 (321 ) 47 70,005 (1,457 ) Total 147 $ 269,903 $ (5,099 ) 198 $ 356,138 $ (10,385 ) 345 $ 626,041 $ (15,484 )
Schedule of Net Investment Income	The following table presents the components of net investment income: For the year ended December 31, 2019 2018 2017 (In Thousands) Investment income $ 31,332 $ 24,342 $ 17,046 Investment expenses (476 ) (804 ) (773 ) Net investment income $ 30,856 $ 23,538 $ 16,273
Schedule of Net Realized Investment Gains (Losses)	The following table presents the components of net realized investment gains: For the year ended December 31, 2019 2018 2017 (In Thousands) Gross realized investment gains $ 561 $ 525 $ 546 Gross realized investment losses (516 ) (468 ) (338 ) Net realized investment gains $ 45 $ 57 $ 208

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Schedule of Fair Value Measurements of Financial Instruments	The following tables present the level within the fair value hierarchy at which our financial instruments were measured: Fair Value Measurements Using Quoted Prices in Significant Other Significant Fair Value As of December 31, 2019 (In Thousands) U.S. Treasury securities and obligations of U.S. government agencies $ 48,929 $ — $ — $ 48,929 Municipal debt securities — 190,216 — 190,216 Corporate debt securities — 684,881 — 684,881 Asset-backed securities — 172,642 — 172,642 Cash, cash equivalents and short-term investments 85,361 — — 85,361 Total assets $ 134,290 $ 1,047,739 $ — $ 1,182,029 Warrant liability — — 7,641 7,641 Total liabilities $ — $ — $ 7,641 $ 7,641 Fair Value Measurements Using Quoted Prices in Significant Other Significant Fair Value As of December 31, 2018 (In Thousands) U.S. Treasury securities and obligations of U.S. government agencies $ 46,830 $ — $ — $ 46,830 Municipal debt securities — 91,257 — 91,257 Corporate debt securities — 543,238 — 543,238 Asset-backed securities — 171,325 — 171,325 Cash, cash equivalents and short-term investments 84,134 — — 84,134 Total assets $ 130,964 $ 805,820 $ — $ 936,784 Warrant liability — — 7,296 7,296 Total liabilities $ — $ — $ 7,296 $ 7,296
Roll-Forward of Level 3 Liabilities Measured at Fair Value	The following is a roll-forward of Level 3 liabilities measured at fair value: For the year ended December 31, 2019 2018 2017 (In Thousands) Balance, January 1 $ 7,296 $ 7,472 $ 3,367 Change in fair value of warrant liability included in earnings 8,657 1,397 4,105 Issuance of common stock on warrant exercise (8,312 ) (1,573 ) — Balance, December 31 $ 7,641 $ 7,296 $ 7,472
Schedule of Key Inputs and Assumptions in Option-Pricing Model	The following table outlines the key inputs and assumptions used to calculate the fair value of the warrant liability in the Black-Scholes option-pricing model as of the dates indicated. As of December 31, 2019 2018 2017 Common stock price $ 33.18 $ 17.85 $ 17.00 Risk free interest rate 1.59 % 2.46 - 2.47% 1.99 % Expected life 2.31 years 2.58 - 3.31 years 3.07 years Expected volatility 41.4 % 41.1 - 42.5% 30.6 % Dividend yield — % — % — %

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Schedule of Future Principal Payments	Future principal payments due under the 2018 Term Loan as of December 31, 2019 are as follows: As of December 31, 2019 Principal (In thousands) 2020 $ 1,500 2021 1,500 2022 1,500 2023 143,250 Total $ 147,750

Reinsurance (Tables)

Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2019
Reinsurance Disclosures [Abstract]
Schedule of Effects of Reinsurance Agreements	The effect of our reinsurance agreements on premiums written and earned is as follows: For the year ended December 31, 2019 December 31, 2018 December 31, 2017 (In Thousands) Net premiums written Direct $ 376,052 $ 287,791 $ 202,586 Ceded (1) (43,400 ) (30,988 ) (28,914 ) Net premiums written $ 332,652 $ 256,803 $ 173,672 Net premiums earned Direct $ 398,303 $ 292,064 $ 192,326 Ceded (1) (53,288 ) (40,867 ) (26,586 ) Net premiums earned $ 345,015 $ 251,197 $ 165,740 (1) Net of profit commission. The following table shows the amounts related to the QSR Transactions: For the year ended December 31, 2019 December 31, 2018 December 31, 2017 (In Thousands) Ceded risk-in-force $ 5,137,249 $ 4,292,450 $ 2,983,353 Ceded premiums earned (89,211 ) (74,068 ) (49,619 ) Ceded claims and claim expenses 3,465 1,763 1,687 Ceding commission earned 17,652 14,585 9,806 Profit commission 50,513 42,846 28,084
Schedule of ILN Transactions	The following table presents the inception date, covered production period, initial and current reinsurance coverage amount, and initial and current first layer retained aggregate loss under each of the ILN Transactions. ( $ values in thousands) Inception Date Covered Production Initial Reinsurance Coverage Current Reinsurance Coverage Initial First Layer Retained Loss Current First Layer Retained Loss 2017 ILN Transaction May 2, 2017 1/1/2013 - 12/31/2016 $ 211,320 $ 61,900 $ 126,793 $ 123,330 2018 ILN Transaction July 25, 2018 1/1/2017 - 5/31/2018 264,545 202,396 125,312 124,594 2019 ILN Transaction July 30, 2019 6/1/2018 - 6/30/2019 326,905 301,396 123,424 123,424

Reserves for Insurance Claims a

Reserves for Insurance Claims and Claim Expenses (Tables)	12 Months Ended
	Dec. 31, 2019
Insurance [Abstract]
Reconciliation of Liability for Insurance Claims and Claims Expenses	The following table provides a reconciliation of the beginning and ending reserve balances for primary insurance claims and claim expenses: For the year ended December 31, 2019 December 31, 2018 December 31, 2017 (In Thousands) Beginning balance $ 12,811 $ 8,761 $ 3,001 Less reinsurance recoverables (1) (3,001 ) (1,902 ) (297 ) Beginning balance, net of reinsurance recoverables 9,810 6,859 2,704 Add claims incurred: Claims and claim expenses incurred: Current year (2) 14,737 7,860 6,140 Prior years (3) (2,230 ) (2,408 ) (801 ) Total claims and claim expenses incurred 12,507 5,452 5,339 Less claims paid: Claims and claim expenses paid: Current year (2) 204 130 27 Prior years (3) 3,849 2,371 1,157 Reinsurance terminations (4) (549 ) — — Total claims and claim expenses paid 3,504 2,501 1,184 Reserve at end of period, net of reinsurance recoverables 18,813 9,810 6,859 Add reinsurance recoverables (1) 4,939 3,001 1,902 Ending balance $ 23,752 $ 12,811 $ 8,761 (1) Related to ceded losses recoverable under the QSR Transactions, included in "Other assets" on the Consolidated Balance Sheets. See Note 6, " Reinsurance " for additional information. (2) Related to insured loans with their most recent defaults occurring in the current year. For example, if a loan defaulted in a prior year and subsequently cured and later re-defaulted in the current year, the default would be included in the current year. Amounts are presented net of reinsurance. (3) Related to insured loans with defaults occurring in prior years, which have been continuously in default before the start of the current year. Amounts are presented net of reinsurance. (4) Represents the settlement of reinsurance recoverables in conjunction with the termination of one reinsurer under the 2016 QSR Transaction on a cut-off basis. See Note 6, " Reinsurance " for additional information.
Schedule of Claims Development Data	The following tables provide claim development data, by accident year and a reconciliation to the reserve for insurance claims and claim expenses. Cumulative Incurred Claims and Allocated Claims Adjustment Expenses, net of Reinsurance (1) As of December 31, 2019 Accident Year 2013 2014 2015 2016 2017 2018 2019 Total of IBNR NODs (2) ($ Values In Thousands) 2013 $ — $ — $ — $ — $ — $ — $ — $ — — 2014 83 34 4 4 4 4 2015 699 664 743 764 894 1 1 2016 2,394 1,568 1,790 1,934 4 5 2017 6,028 3,475 3,570 30 34 2018 7,779 5,271 155 174 2019 14,391 $ 1,097 1,234 Total $ 26,064 $ 1,287 1,448 (1) Amounts include case and IBNR reserves. (2) The number of NODs outstanding as of December 31, 2019 is the total number of loans in default over 60 days. Cumulative Paid Claims and Claims Adjustment Expenses, net of Reinsurance Accident Year 2013 2014 2015 2016 2017 2018 2019 (In Thousands) 2013 $ — $ — $ — $ — $ — $ — $ — 2014 — 4 4 4 4 4 2015 50 246 684 720 804 2016 171 890 1,596 1,826 2017 27 1,655 2,925 2018 130 1,981 2019 69 Total $ 7,609
Schedule of Reconciliation of Claims Development to Liability	Reconciliation of Disclosure of Incurred and Paid Claims Development to the Liability for Unpaid Claims and Claim Adjustment Expenses (In Thousands) As of December 31, 2019 Cumulative Incurred Claims and Allocated Claims Adjustment Expenses, net of Reinsurance $ 26,064 Cumulative Paid Claims and Claims Adjustment Expenses, net of Reinsurance 7,609 Liabilities for unpaid claims and allocated claims adjustment expenses, net of reinsurance 18,455 Reinsurance recoverable on unpaid claims 4,939 Unallocated claims adjustment expenses 358 Total gross liability for unpaid claims and claim adjustment expenses $ 23,752
Schedule of Historical Claims Duration	The following table shows, on average, the percentage of claims and allocated claims adjustment expenses paid over the years after a claim is incurred. Average annual percentage payout of incurred claims and allocated claims adjustment expenses by age, net of reinsurance Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Claims duration disclosure 3% 38% 91% 96% 95% 100%

Earnings per Share (Tables)

Earnings per Share (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table reconciles the net income and the weighted average shares of common stock outstanding used in the computations of basic and diluted EPS of common stock. For the year ended December 31, 2019 2018 2017 (In Thousands, except for per share data) Net income $ 171,957 $ 107,927 $ 22,050 Basic weighted average shares outstanding 67,573 65,019 59,816 Basic earnings per share $ 2.54 $ 1.66 $ 0.37 Net income $ 171,957 $ 107,927 $ 22,050 Gain from change in fair value of warrant liability — — — Diluted net income $ 171,957 $ 107,927 $ 22,050 Basic weighted average shares outstanding 67,573 65,019 59,816 Dilutive effect of issuable shares 2,148 2,633 2,370 Diluted weighted average shares outstanding 69,721 67,652 62,186 Diluted earnings per share $ 2.47 $ 1.60 $ 0.35 Anti-dilutive shares 565 843 995

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Schedule of Stock Option Activity	A summary of option activity during the years ended December 31, 2019 , 2018 and 2017 , is as follows: For the year ended December 31, 2019 Shares Weighted Average Grant Date Fair Value per Share Weighted Average Exercise Price (Shares in Thousands) Options outstanding at December 31, 2018 2,882 $ 4.24 $ 11.42 Options granted 163 8.85 22.19 Options exercised (1,117 ) 3.88 10.19 Options forfeited — — — Options expired — — — Options outstanding at December 31, 2019 1,928 $ 4.84 $ 13.04 For the Year Ended December 31, 2018 Shares Weighted Average Grant Date Fair Value per Share Weighted Average Exercise Price (Shares in Thousands) Options outstanding at December 31, 2017 3,311 $ 3.95 $ 10.41 Options granted 383 6.32 18.08 Options exercised (803 ) 4.06 10.43 Options forfeited — — — Options expired (9 ) 4.05 10.51 Options outstanding at December 31, 2018 2,882 $ 4.24 $ 11.42 For the year ended December 31, 2017 Shares Weighted Average Grant Date Fair Value per Share Weighted Average Exercise Price (Shares in Thousands) Options outstanding at December 31, 2016 3,026 $ 3.97 $ 10.27 Options granted 574 3.89 11.06 Options exercised (273 ) 3.93 10.17 Options forfeited (1 ) 4.97 12.32 Options expired (15 ) 4.76 12.02 Options outstanding at December 31, 2017 3,311 $ 3.95 $ 10.41
Schedule of Stock Options Valuation Assumptions	The estimated grant date fair values of the stock options granted during the years ended December 31, 2019 , 2018 , and 2017 were calculated using the Black-Scholes valuation model based on the following assumptions. For the years ended December 31, 2019 2018 2017 Expected life 6 years 6 years 6 years Risk free interest rate 2.57% 2.66-2.89% 2.04-2.08% Dividend yield — % — % — % Expected stock price volatility 36.8 % 30.1-30.6% 30.5-32.7%
Schedule of Restricted Stock Units Activity	A summary of RSU activity during the years ended December 31, 2019, 2018 and 2017 is as follows: For the year ended December 31, 2019 Shares Weighted Average Grant Date Fair Value per Share (Shares in Thousands) Non-vested restricted stock units at December 31, 2018 1,753 $ 12.06 Restricted stock units granted 470 24.42 Restricted stock units vested (970 ) 9.71 Restricted stock units forfeited (51 ) 15.06 Non-vested restricted stock units at December 31, 2019 1,202 $ 18.67 For the year ended December 31, 2018 Shares Weighted Average Grant Date Fair Value per Share (Shares in Thousands) Non-vested restricted stock units at December 31, 2017 2,065 $ 8.15 Restricted stock units granted 701 17.22 Restricted stock units vested (913 ) 7.42 Restricted stock units forfeited (100 ) 9.89 Non-vested restricted stock units at December 31, 2018 1,753 $ 12.06 For the year ended December 31, 2017 Shares Weighted Average Grant Date Fair Value per Share (Shares in Thousands) Non-vested restricted stock units at December 31, 2016 2,538 $ 6.01 Restricted stock units granted 988 11.22 Restricted stock units vested (1,367 ) 6.67 Restricted stock units forfeited (94 ) 8.96 Non-vested restricted stock units at December 31, 2017 2,065 $ 8.15

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit)	Total income tax expense consists of the following components: For the year ended December 31, 2019 2018 2017 (In Thousands) Current $ (386 ) $ 1,677 $ 778 Deferred 45,082 26,357 29,964 Total income tax expense $ 44,696 $ 28,034 $ 30,742
Schedule of Effective Income Tax Rate Reconciliation	The following table presents a reconciliation between the federal statutory income tax rate and our effective income tax rate: For the year ended December 31, 2019 2018 2017 Federal statutory income tax rate 21.0 % 21.0 % 35.0 % State provision 0.5 0.7 0.6 Share-based and other compensation (1.7 ) (1.4 ) (4.7 ) Warrant gain/loss 0.9 0.2 1.8 Re-measurement from change in federal statutory rate — — 25.7 Other (1) (0.1 ) 0.1 (0.2 ) Effective income tax rate 20.6 % 20.6 % 58.2 % (1) Prior periods have been reclassified for consistency and presentation purposes.
Schedule of Deferred Tax Assets and Liabilities	The components of our net deferred tax asset are summarized as follows: As of December 31, 2019 2018 Deferred tax asset (In Thousands) Net operating loss carry forwards $ 9,244 $ 6,896 Share-based compensation 5,959 6,791 Unearned premium reserve 5,213 5,568 Accrued expenses 4,539 5,495 Capitalized start-up costs 634 727 Deferred ceding commissions 566 821 Unrealized loss on investments — 2,923 Other 772 364 Total gross deferred tax asset 26,927 29,585 Less: valuation allowance (7,857 ) (8,136 ) Total deferred tax asset 19,070 21,449 Deferred tax liability Contingency reserve (47,730 ) (8,149 ) Deferred acquisition costs (12,902 ) (10,145 ) Unrealized gain on investments (7,634 ) — Capitalized software (5,107 ) (4,757 ) Intangible assets (111 ) (82 ) Other (1,946 ) (1,056 ) Total deferred tax liability (75,430 ) (24,189 ) Net deferred income tax (liability) $ (56,360 ) $ (2,740 )

Software and Equipment (Tables)

Software and Equipment (Tables)	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Schedule of Equipment and Software	Software and equipment, net of accumulated amortization and depreciation, as of December 31, 2019 and 2018 , consists of the following: December 31, 2019 December 31, 2018 (In Thousands) Software $ 46,522 $ 38,450 Equipment 8,992 7,035 Leasehold improvements 3,442 3,491 Subtotal 58,956 48,976 Accumulated amortization and depreciation (32,860 ) (24,211 ) Software and equipment, net $ 26,096 $ 24,765

Intangible Assets and Goodwill

Intangible Assets and Goodwill (Tables)	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Identifiable Intangible Assets and Goodwill	Intangible assets and goodwill consist of identifiable intangible assets and goodwill purchased in connection with the acquisition of our insurance subsidiaries. Intangible assets and goodwill as of both December 31, 2019 and 2018 were as follows: (In Thousands) Expected Lives Goodwill $ 3,244 Indefinite State licenses 260 Indefinite GSE applications 130 Indefinite Total intangible assets and goodwill $ 3,634

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Summary of Right-of-Use Asset and Lease Liability Activity and Assumptions	The following table provides a summary of our ROU asset and lease liability assumptions as of December 31, 2019 : Weighted-average remaining lease term 3.2 years Weighted-average discount rate 6.21 %
Schedule of Future Payments Due Under Operating Leases	Future payments due under our existing operating leases as of December 31, 2019 are as follows: Years ending December 31, (In Thousands) 2020 $ 2,537 2021 2,609 2022 2,574 2023 462 Total undiscounted lease payments 8,182 Less effects of discounting (780 ) Present value of lease payments $ 7,402
Schedule of Future Minimum Lease Payments	As of December 31, 2018, the future minimum lease payments as accounted for prior to our adoption of ASU 2016-02, Leases (Topic 842) were as follows: Years ending December 31, (In Thousands) 2019 $ 2,346 2020 2,417 2021 2,489 2022 2,564 2023 463 Totals $ 10,279

Regulatory Information (Tables)

Regulatory Information (Tables)	12 Months Ended
	Dec. 31, 2019
Insurance [Abstract]
Schedule of Combined Statutory Net Gain (Loss), Statutory Surplus, Contingency Reserve and RTC Ratios	NMIC and Re One's combined statutory net gain (loss), statutory surplus, contingency reserve and risk-to-capital (RTC) ratios as of and for the years ended December 31, 2019 , 2018 and 2017 were as follows: As of and for the year ended December 31, 2019 2018 2017 (In Thousands) Statutory net gain (loss) $ 15,233 $ (19,784 ) $ (35,946 ) Statutory surplus 449,602 430,785 371,084 Contingency reserve 531,825 332,702 186,641 Risk-to-capital 15.8:1 13.1:1 13.2:1

Quarterly Financial Data (Una_2

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	2019 Quarters 2019 First Second Third Fourth Year (In Thousands, except per share data) Net premiums earned $ 73,868 $ 83,249 $ 92,381 $ 95,517 $ 345,015 Net investment income 7,383 7,629 7,882 7,962 30,856 Net realized investment (losses) gains (187 ) (113 ) 81 264 45 Other revenues 42 415 1,244 1,154 2,855 Insurance claims and claim expenses 2,743 2,923 2,572 4,269 12,507 Underwriting and operating expenses (1) 30,800 32,190 32,335 31,296 126,621 Service expenses (1) 49 353 909 937 2,248 Interest expense 3,061 3,071 2,979 2,974 12,085 Loss (gain) from change in fair value of warrant liability 5,479 1,685 (1,139 ) 2,632 8,657 Pre-tax income 38,974 50,958 63,932 62,789 216,653 Income tax expense 6,075 11,858 14,169 12,594 44,696 Net income $ 32,899 $ 39,100 $ 49,763 $ 50,195 $ 171,957 Income per share: (2) Basic earnings per share $ 0.49 $ 0.58 $ 0.73 $ 0.74 $ 2.54 Diluted earnings per share $ 0.48 $ 0.56 $ 0.69 $ 0.71 $ 2.47 Weighted average common shares outstanding - basic 66,692 67,590 67,849 68,140 67,573 Weighted average common shares outstanding - diluted 68,996 69,590 70,137 70,276 69,721 (1) Certain "Underwriting and operating expenses" have been reclassified as "Service expenses" in prior periods. (2) Due to the use of weighted average shares outstanding when calculating EPS , the sum of quarterly per share data may not equal the per share data for the year. 2018 Quarters 2018 First Second Third Fourth Year (In Thousands, except per share data) Net premiums earned $ 54,914 $ 61,615 $ 65,407 $ 69,261 $ 251,197 Net investment income 4,574 5,735 6,277 6,952 23,538 Net realized investment gains (losses) — 59 (8 ) 6 57 Other revenues 64 44 85 40 233 Insurance claims and claim expenses 1,569 643 1,099 2,141 5,452 Underwriting and operating expenses (1) 28,346 28,958 30,323 29,339 116,966 Service expenses (1) 107 62 56 45 270 Interest expense 3,419 5,560 2,972 3,028 14,979 (Gain) loss from change in fair value of warrant liability (420 ) (109 ) 5,464 (3,538 ) 1,397 Pre-tax income 26,531 32,339 31,847 45,244 135,961 Income tax expense 4,176 7,098 7,036 9,724 28,034 Net income $ 22,355 $ 25,241 $ 24,811 $ 35,520 $ 107,927 Income per share: (2) Basic earnings per share $ 0.36 $ 0.38 $ 0.38 $ 0.54 $ 1.66 Diluted earnings per share $ 0.34 $ 0.37 $ 0.36 $ 0.46 $ 1.60 Weighted average common shares outstanding - basic 62,099 65,664 65,948 66,308 65,019 Weighted average common shares outstanding - diluted 65,697 68,616 68,844 69,013 67,652 (1) Certain "Underwriting and operating expenses" have been reclassified as "Service expenses" in prior periods. (2) Due to the use of weighted average shares outstanding when calculating EPS, the sum of quarterly per share data may not equal the per share data for the year.

Organization and Basis of Pre_2

Organization and Basis of Presentation (Details)	Dec. 31, 2019state
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of states in which the entity operates	50

Summary of Accounting Policie_2

Summary of Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2019USD ($)entity	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Jan. 01, 2019USD ($)
Finite-Lived Intangible Assets [Line Items]
IBNR default period (at least)	60 days
Amortization of deferred acquisition expense	$ 8,400,000	$ 8,100,000	$ 5,800,000
Premium deficiency reserve expense	$ 0	$ 0	$ 0
Mortgage insurance premiums receivable threshold for write off (in days)	120 days
Number of special purpose reinsurance entities | entity	3
Right-of-use lease assets	$ 6,400,000
Operating lease liabilities	$ 7,402,000
ASU No. 2016-02
Finite-Lived Intangible Assets [Line Items]
Right-of-use lease assets				$ 7,600,000
Operating lease liabilities				$ 7,600,000
Software | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	3 years
Software | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	5 years
Equipment | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	3 years
Equipment | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	5 years
Geographic Concentration Risk | Risk-in-Force
Finite-Lived Intangible Assets [Line Items]
Concentration risk	12.00%

Investments - Fair Values and G

Investments - Fair Values and Gross Unrealized Gains and Losses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Total investments	$ 1,113,779	$ 924,987
Gross unrealized gains	28,579	1,987
Gross unrealized losses	(1,418)	(15,484)
Fair value of securities	1,140,940	911,490
U.S. Treasury securities and obligations of U.S. government agencies
Debt Securities, Available-for-sale [Line Items]
Total investments	48,203	48,171
Gross unrealized gains	784	35
Gross unrealized losses	(58)	(1,376)
Fair value of securities	48,929	46,830
Municipal debt securities
Debt Securities, Available-for-sale [Line Items]
Total investments	189,530	92,014
Gross unrealized gains	1,721	206
Gross unrealized losses	(1,035)	(963)
Fair value of securities	190,216	91,257
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Total investments	661,719	554,079
Gross unrealized gains	23,373	847
Gross unrealized losses	(211)	(11,688)
Fair value of securities	684,881	543,238
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Total investments	170,153	171,990
Gross unrealized gains	2,603	792
Gross unrealized losses	(114)	(1,457)
Fair value of securities	172,642	171,325
Total bonds
Debt Securities, Available-for-sale [Line Items]
Total investments	1,069,605	866,254
Gross unrealized gains	28,481	1,880
Gross unrealized losses	(1,418)	(15,484)
Fair value of securities	1,096,668	852,650
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Total investments	44,174	58,733
Gross unrealized gains	98	107
Gross unrealized losses	0	0
Fair value of securities	$ 44,272	$ 58,840

Investments - Corporate Debt Se

Investments - Corporate Debt Securities by Industry Group (Details)	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Corporate debt securities as component of total (percent)	100.00%	100.00%
Financial
Debt Securities, Available-for-sale [Line Items]
Corporate debt securities as component of total (percent)	38.00%	38.00%
Consumer
Debt Securities, Available-for-sale [Line Items]
Corporate debt securities as component of total (percent)	26.00%	27.00%
Communications
Debt Securities, Available-for-sale [Line Items]
Corporate debt securities as component of total (percent)	10.00%	12.00%
Utilities
Debt Securities, Available-for-sale [Line Items]
Corporate debt securities as component of total (percent)	9.00%	7.00%
Industrial
Debt Securities, Available-for-sale [Line Items]
Corporate debt securities as component of total (percent)	8.00%	7.00%
Technology
Debt Securities, Available-for-sale [Line Items]
Corporate debt securities as component of total (percent)	7.00%	6.00%
Energy
Debt Securities, Available-for-sale [Line Items]
Corporate debt securities as component of total (percent)	2.00%	2.00%
Other
Debt Securities, Available-for-sale [Line Items]
Corporate debt securities as component of total (percent)	0.00%	1.00%

Investments - Narrative (Detail

Investments - Narrative (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Unrealized loss position, accumulated loss		$ 15,484,000		$ 1,418,000
Unrealized loss position, 12 months or greater		(10,385,000)		(84,000)
Other-than-temporary impairment	$ 400,000	0	$ 100,000
U.S. Treasury securities and obligations of U.S. government agencies
Debt Securities, Available-for-sale [Line Items]
Cash and investments held with various state insurance departments		5,300,000		5,500,000
Unrealized loss position, accumulated loss		1,376,000		58,000
Unrealized loss position, 12 months or greater		$ (1,376,000)		$ 0

Investments - Scheduled Maturit

Investments - Scheduled Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Amortized Cost
Due in one year or less	$ 138,776	$ 76,087
Due after one through five years	406,986	352,282
Due after five through ten years	380,737	318,728
Due after ten years	17,127	5,900
Asset-backed securities	170,153	171,990
Total investments	1,113,779	924,987
Fair Value
Due in one year or less	139,113	76,104
Due after one through five years	417,208	347,701
Due after five through ten years	394,180	310,633
Due after ten years	17,797	5,727
Asset-backed securities	172,642	171,325
Total investments	$ 1,140,940	$ 911,490

Investments - Aging of Unrealiz

Investments - Aging of Unrealized Losses (Details) $ in Thousands	Dec. 31, 2019USD ($)security	Dec. 31, 2018USD ($)security
Number of Securities
Less Than 12 Months | security	49	147
12 Months or Greater | security	16	198
Total | security	65	345
Fair Value
Less Than 12 Months	$ 154,562	$ 269,903
12 Months or Greater	27,963	356,138
Total	182,525	626,041
Unrealized Losses
Less Than 12 Months	(1,334)	(5,099)
12 Months or Greater	(84)	(10,385)
Total	$ (1,418)	$ (15,484)
U.S. Treasury securities and obligations of U.S. government agencies
Number of Securities
Less Than 12 Months | security	4	0
12 Months or Greater | security	0	19
Total | security	4	19
Fair Value
Less Than 12 Months	$ 12,001	$ 0
12 Months or Greater	0	41,817
Total	12,001	41,817
Unrealized Losses
Less Than 12 Months	(58)	0
12 Months or Greater	0	(1,376)
Total	$ (58)	$ (1,376)
Municipal debt securities
Number of Securities
Less Than 12 Months | security	26	4
12 Months or Greater | security	1	31
Total | security	27	35
Fair Value
Less Than 12 Months	$ 92,844	$ 7,409
12 Months or Greater	999	58,658
Total	93,843	66,067
Unrealized Losses
Less Than 12 Months	(1,034)	(11)
12 Months or Greater	(1)	(952)
Total	$ (1,035)	$ (963)
Corporate debt securities
Number of Securities
Less Than 12 Months | security	10	118
12 Months or Greater | security	14	126
Total | security	24	244
Fair Value
Less Than 12 Months	$ 30,481	$ 226,477
12 Months or Greater	23,976	221,675
Total	54,457	448,152
Unrealized Losses
Less Than 12 Months	(140)	(3,952)
12 Months or Greater	(71)	(7,736)
Total	$ (211)	$ (11,688)
Asset-backed securities
Number of Securities
Less Than 12 Months | security	9	25
12 Months or Greater | security	1	22
Total | security	10	47
Fair Value
Less Than 12 Months	$ 19,236	$ 36,017
12 Months or Greater	2,988	33,988
Total	22,224	70,005
Unrealized Losses
Less Than 12 Months	(102)	(1,136)
12 Months or Greater	(12)	(321)
Total	$ (114)	$ (1,457)

Investments - Net Investment In

Investments - Net Investment Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Investment income	$ 31,332	$ 24,342	$ 17,046
Investment expenses	(476)	(804)	(773)
Net investment income	$ 30,856	$ 23,538	$ 16,273

Investments - Net Realized Inve

Investments - Net Realized Investments Gains (Losses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Gross realized investment gains	$ 561	$ 525	$ 546
Gross realized investment losses	(516)	(468)	(338)
Net realized investment gains	$ 45	$ 57	$ 208

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Assets and Liabilities at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	$ 1,140,940	$ 911,490
U.S. Treasury securities and obligations of U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	48,929	46,830
Municipal debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	190,216	91,257
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	684,881	543,238
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	172,642	171,325
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash, cash equivalents and short-term investments	85,361	84,134
Total assets	1,182,029	936,784
Total liabilities	7,641	7,296
Recurring | U.S. Treasury securities and obligations of U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	48,929	46,830
Recurring | Municipal debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	190,216	91,257
Recurring | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	684,881	543,238
Recurring | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	172,642	171,325
Recurring | Warrant liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liability	7,641	7,296
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash, cash equivalents and short-term investments	85,361	84,134
Total assets	134,290	130,964
Total liabilities	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury securities and obligations of U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	48,929	46,830
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Warrant liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liability	0	0
Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash, cash equivalents and short-term investments	0	0
Total assets	1,047,739	805,820
Total liabilities	0	0
Recurring | Significant Other Observable Inputs (Level 2) | U.S. Treasury securities and obligations of U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	0	0
Recurring | Significant Other Observable Inputs (Level 2) | Municipal debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	190,216	91,257
Recurring | Significant Other Observable Inputs (Level 2) | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	684,881	543,238
Recurring | Significant Other Observable Inputs (Level 2) | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	172,642	171,325
Recurring | Significant Other Observable Inputs (Level 2) | Warrant liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liability	0	0
Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash, cash equivalents and short-term investments	0	0
Total assets	0	0
Total liabilities	7,641	7,296
Recurring | Significant Unobservable Inputs (Level 3) | U.S. Treasury securities and obligations of U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Municipal debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Warrant liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liability	$ 7,641	$ 7,296

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Rollfoward of Level 3 Liabilities (Details) - Significant Unobservable Inputs (Level 3) - Warrant liability - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 7,296	$ 7,472	$ 3,367
Change in fair value of warrant liability included in earnings	8,657	1,397	4,105
Issuance of common stock on warrant exercise	(8,312)	(1,573)	0
Ending balance	$ 7,641	$ 7,296	$ 7,472

Fair Value of Financial Instr_5

Fair Value of Financial Instruments - Valuation Assumptions for Warrant Liabilities (Details) - Significant Unobservable Inputs (Level 3) - Valuation Technique, Option Pricing Model	Dec. 31, 2019$ / shares	Dec. 31, 2018$ / shares	Dec. 31, 2017$ / shares
Common stock price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, measurement input	33.18	17.85	17
Risk free interest rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, measurement input	0.0159		0.0199
Risk free interest rate | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, measurement input		0.0246
Risk free interest rate | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, measurement input		0.0247
Expected life
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, expected life (in years)	2 years 3 months 22 days		3 years 26 days
Expected life | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, expected life (in years)		2 years 6 months 29 days
Expected life | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, expected life (in years)		3 years 3 months 22 days
Expected volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, measurement input	0.414		0.306
Expected volatility | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, measurement input		0.411
Expected volatility | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, measurement input		0.425
Dividend yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, measurement input	0	0	0

Fair Value of Financial Instr_6

Fair Value of Financial Instruments - Narrative (Details) $ in Thousands	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Term loan	$ 145,764	$ 146,757
2018 Term Loan | Secured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Term loan		146,800
Unamortized issuance cost and original issue discount	2,000	2,500
2018 Term Loan | Secured Debt | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of term loan	$ 147,800	$ 146,300
Valuation Technique, Option Pricing Model | Expected life | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liability, expected life (in years)	2 years 3 months 22 days		3 years 26 days
Valuation Technique, Option Pricing Model | Expected volatility | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liability, measurement input	0.414		0.306
Valuation Technique, Option Pricing Model | Risk free interest rate | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liability, measurement input	0.0159		0.0199
Maximum | Valuation Technique, Option Pricing Model | Expected life | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liability, expected life (in years)		3 years 3 months 22 days
Maximum | Valuation Technique, Option Pricing Model | Expected volatility | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liability, measurement input		0.425
Maximum | Valuation Technique, Option Pricing Model | Risk free interest rate | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liability, measurement input		0.0247
Minimum | Valuation Technique, Option Pricing Model | Expected life | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liability, expected life (in years)		2 years 6 months 29 days
Minimum | Valuation Technique, Option Pricing Model | Expected volatility | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liability, measurement input		0.411
Minimum | Valuation Technique, Option Pricing Model | Risk free interest rate | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liability, measurement input		0.0246

Debt - Narrative (Details)

Debt - Narrative (Details) - USD ($)

May 24, 2018

Dec. 31, 2019

Sep. 30, 2019

Jun. 30, 2019

Mar. 31, 2019

Dec. 31, 2018

Sep. 30, 2018

Jun. 30, 2018

Mar. 31, 2018

Dec. 31, 2019

Dec. 31, 2018

Dec. 31, 2017

Nov. 10, 2015

Debt Instrument [Line Items]

Term loan

$ 147,750,000

$ 147,750,000

Interest expense

2,974,000

$ 2,979,000

$ 3,071,000

$ 3,061,000

$ 3,028,000

$ 2,972,000

$ 5,560,000

$ 3,419,000

$ 12,085,000

$ 14,979,000

$ 13,528,000

Secured Debt | 2018 Term Loan

Debt Instrument [Line Items]

Debt instrument face amount

$ 150,000,000

Debt instrument term (years)

5 years

Frequency of periodic payment

Quarterly

Periodic payment of principal

$ 400,000

Interest expense

11,200,000

Unamortized issuance cost and original issue discount

2,000,000

$ 2,500,000

$ 2,000,000

$ 2,500,000

Debt instrument covenant, maximum debt-to-total capitalization ratio

35.00%

Secured Debt | 2018 Term Loan | LIBOR

Debt Instrument [Line Items]

Variable rate floor (percent)

1.00%

Basis spread on variable rate (percent)

4.75%

Interest rate during period (percent)

6.55%

Senior Secured Debt | 2015 Term Loan

Debt Instrument [Line Items]

Debt instrument face amount

$ 150,000,000

Revolving Credit Facility | 2018 Revolving Credit Facility

Debt Instrument [Line Items]

Debt instrument term (years)

3 years

Credit facility borrowing capacity

$ 85,000,000

Borrowings outstanding

0

$ 0

Debt instrument covenant, maximum debt-to-total capitalization ratio

35.00%

Commitment fee (percent)

0.40%

Commitment fees in interest expense

$ 400,000

Deferred debt issuance costs

$ 1,500,000

Amortization of deferred issuance costs

500,000

Remaining deferred issuance costs, net of accumulated amortization

$ 700,000

$ 700,000

Revolving Credit Facility | 2018 Revolving Credit Facility | Minimum

Debt Instrument [Line Items]

Commitment fee (percent)

0.30%

Revolving Credit Facility | 2018 Revolving Credit Facility | Maximum

Debt Instrument [Line Items]

Commitment fee (percent)

0.60%

Revolving Credit Facility | 2018 Revolving Credit Facility | Base Rate

Debt Instrument [Line Items]

Variable rate floor (percent)

1.00%

Revolving Credit Facility | 2018 Revolving Credit Facility | Base Rate | Minimum

Debt Instrument [Line Items]

Basis spread on variable rate (percent)

1.00%

Revolving Credit Facility | 2018 Revolving Credit Facility | Base Rate | Maximum

Debt Instrument [Line Items]

Basis spread on variable rate (percent)

2.50%

Revolving Credit Facility | 2018 Revolving Credit Facility | Eurodollar

Debt Instrument [Line Items]

Variable rate floor (percent)

0.00%

Revolving Credit Facility | 2018 Revolving Credit Facility | Eurodollar | Minimum

Debt Instrument [Line Items]

Basis spread on variable rate (percent)

2.00%

Revolving Credit Facility | 2018 Revolving Credit Facility | Eurodollar | Maximum

Debt Instrument [Line Items]

Basis spread on variable rate (percent)

3.50%

Debt - Schedule of Future Princ

Debt - Schedule of Future Principal Payments (Details) $ in Thousands	Dec. 31, 2019USD ($)
As of December 31, 2019
2020	$ 1,500
2021	1,500
2022	1,500
2023	143,250
Total	$ 147,750

Reinsurance - Effect of Reinsur

Reinsurance - Effect of Reinsurance Agreements on Premiums Written and Earned (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net premiums written
Direct									$ 376,052	$ 287,791	$ 202,586
Ceded									(43,400)	(30,988)	(28,914)
Net premiums written									332,652	256,803	173,672
Net premiums earned
Direct									398,303	292,064	192,326
Ceded									(53,288)	(40,867)	(26,586)
Net premiums earned	$ 95,517	$ 92,381	$ 83,249	$ 73,868	$ 69,261	$ 65,407	$ 61,615	$ 54,914	$ 345,015	$ 251,197	$ 165,740

Reinsurance - Narrative (Detail

Reinsurance - Narrative (Details) - USD ($) $ in Thousands	Apr. 01, 2019	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Ceded Credit Risk [Line Items]
Restricted cash		$ 2,662	$ 2,662	$ 1,414
Reinsurance recoverable on unpaid claims		$ 4,939	$ 4,939	3,001	$ 1,902	$ 297
ILN Transactions
Ceded Credit Risk [Line Items]
Optional termination right, percent of reinsurance coverage threshold		10.00%	10.00%
Third-Party Reinsurers | 2017 ILN Transaction
Ceded Credit Risk [Line Items]
Risk premiums paid			$ 14,600	$ 9,600	$ 5,000
Third-Party Reinsurers | QSR Transactions
Ceded Credit Risk [Line Items]
Ceding commissions under QSR Transaction				20.00%
Third-Party Reinsurers | 2018 QSR Transaction
Ceded Credit Risk [Line Items]
Threshold for loss ratio on loans to qualify for profit commission				61.00%
Reinsurance recoverable on unpaid claims		$ 2,100	$ 2,100
Third-Party Reinsurers | Risk Written Policies in 2018
Ceded Credit Risk [Line Items]
Premiums of premiums earned under QSR Transaction				25.00%
Third-Party Reinsurers | Risk Written Policies in 2019
Ceded Credit Risk [Line Items]
Percent of premiums ceded under QSR Transaction			20.00%
Third-Party Reinsurers | 2016 QSR Transaction
Ceded Credit Risk [Line Items]
Percent of premiums ceded under QSR Transaction		20.50%	25.00%
Previously Ceded Primary Risk-In-Force Recaptured	$ 500,000
Threshold for loss ratio on loans to qualify for profit commission				60.00%
Reinsurance recoverable on unpaid claims		$ 2,800	$ 2,800
Third-Party Reinsurers | Existing Risk Written Policies
Ceded Credit Risk [Line Items]
Percent of premiums ceded under QSR Transaction					25.00%
Third-Party Reinsurers | Fannie Mae
Ceded Credit Risk [Line Items]
Percent of premiums ceded under QSR Transaction			100.00%
Third-Party Reinsurers | Maximum | ILN Transactions
Ceded Credit Risk [Line Items]
Reinsurance coverage, term of underlying mortgage amortization (in years)			10 years
Third-Party Reinsurers | Maximum | 2017 ILN Transaction
Ceded Credit Risk [Line Items]
Anticipated payment related to annual operating expenses			$ 300
Third-Party Reinsurers | Maximum | 2018 ILN Transaction
Ceded Credit Risk [Line Items]
Anticipated payment related to annual operating expenses			$ 250

Reinsurance - ILN Transactions

Reinsurance - ILN Transactions (Details) - USD ($) $ in Thousands	Jul. 30, 2019	Jul. 25, 2018	May 02, 2017
2017 ILN Transaction
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Initial Reinsurance Coverage			$ 211,320
Current Reinsurance Coverage			61,900
Initial First Layer Retained Loss			126,793
Current First Layer Retained Loss			$ 123,330
2018 ILN Transaction
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Initial Reinsurance Coverage		$ 264,545
Current Reinsurance Coverage		202,396
Initial First Layer Retained Loss		125,312
Current First Layer Retained Loss		$ 124,594
2019 ILN Transaction
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Initial Reinsurance Coverage	$ 326,905
Current Reinsurance Coverage	301,396
Initial First Layer Retained Loss	123,424
Current First Layer Retained Loss	$ 123,424

Reinsurance - Amounts Ceded Rel

Reinsurance - Amounts Ceded Related to QSR Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Ceded Credit Risk [Line Items]
Ceded premiums earned	$ (53,288)	$ (40,867)	$ (26,586)
Third-Party Reinsurers
Ceded Credit Risk [Line Items]
Ceded risk-in-force	5,137,249	4,292,450	2,983,353
Ceded premiums earned	(89,211)	(74,068)	(49,619)
Ceded claims and claim expenses	3,465	1,763	1,687
Ceding commission earned	17,652	14,585	9,806
Profit commission	$ 50,513	$ 42,846	$ 28,084

Reserves for Insurance Claims_2

Reserves for Insurance Claims and Claim Expenses - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)loanclaim	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Liability for Claims and Claims Adjustment Expense [Line Items]
IBNR default period (at least)	60 days
Reserve for insurance claims and claim expenses	$ 23,752	$ 12,811	$ 8,761	$ 3,001
Primary loans in default | loan	1,448
Number of claims paid | claim	152
Claims paid, including amounts covered by insurance	$ 5,000
Favorable prior year development	2,230	$ 2,408	$ 801
Reserve for prior year insurance claims and claims expense	$ 5,200
Fannie Mae
Liability for Claims and Claims Adjustment Expense [Line Items]
Number of loans in pool past due 60 days or more | loan	46
Risk-in-Force of loans in pool past due 60 days or more	$ 3,000
Loan-to-value ratio (less than)	0.80
Claims applied to pool deductible	$ 800
Deductible on policy	9,500
2016 QSR Transaction
Liability for Claims and Claims Adjustment Expense [Line Items]
Reserve for insurance claims and claim expenses	$ 1,000
Number of covered claims included in number of claims paid | claim	142
2016 QSR Transaction | Fannie Mae
Liability for Claims and Claims Adjustment Expense [Line Items]
Percent of pool RIF reinsured	100.00%

Reserves for Insurance Claims_3

Reserves for Insurance Claims and Claim Expenses - Reconciliation of Reserve Balances for Insurance Claims Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning balance	$ 12,811	$ 8,761	$ 3,001
Less reinsurance recoverables	(3,001)	(1,902)	(297)
Beginning balance, net of reinsurance recoverables	9,810	6,859	2,704
Claims and claim expenses incurred:
Current year	14,737	7,860	6,140
Prior years	(2,230)	(2,408)	(801)
Total claims and claims expenses incurred	12,507	5,452	5,339
Claims and claim expenses paid:
Current year	204	130	27
Prior years	3,849	2,371	1,157
Reinsurance terminations	(549)	0	0
Total claims and claim expenses paid	3,504	2,501	1,184
Reserve at end of period, net of reinsurance recoverables	18,813	9,810	6,859
Add reinsurance recoverables	(4,939)	(3,001)	(1,902)
Ending balance	$ 23,752	$ 12,811	$ 8,761

Reserves for Insurance Claims_4

Reserves for Insurance Claims and Claim Expenses - Claim Development by Accident Year and Reconciliation of Reserve for Insurance Claims and Claims Expense (Details) - Financial Guarantee Insurance Product Line $ in Thousands	Dec. 31, 2019USD ($)claim	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Claims Development [Line Items]
Cumulative Incurred Claims and Allocated Claims Adjustment Expenses, net of Reinsurance	$ 26,064
Total of IBNR	$ 1,287
NODs | claim	1,448
Cumulative Paid Claims and Claims Adjustment Expenses, net of Reinsurance	$ 7,609
2013
Claims Development [Line Items]
Cumulative Incurred Claims and Allocated Claims Adjustment Expenses, net of Reinsurance	0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Total of IBNR	$ 0
NODs | claim	0
Cumulative Paid Claims and Claims Adjustment Expenses, net of Reinsurance	$ 0	0	0	0	0	0	$ 0
2014
Claims Development [Line Items]
Cumulative Incurred Claims and Allocated Claims Adjustment Expenses, net of Reinsurance	4	4	4	4	34	83
Total of IBNR
NODs | claim
Cumulative Paid Claims and Claims Adjustment Expenses, net of Reinsurance	$ 4	4	4	4	4	$ 0
2015
Claims Development [Line Items]
Cumulative Incurred Claims and Allocated Claims Adjustment Expenses, net of Reinsurance	894	764	743	664	699
Total of IBNR	$ 1
NODs | claim	1
Cumulative Paid Claims and Claims Adjustment Expenses, net of Reinsurance	$ 804	720	684	246	$ 50
2016
Claims Development [Line Items]
Cumulative Incurred Claims and Allocated Claims Adjustment Expenses, net of Reinsurance	1,934	1,790	1,568	2,394
Total of IBNR	$ 4
NODs | claim	5
Cumulative Paid Claims and Claims Adjustment Expenses, net of Reinsurance	$ 1,826	1,596	890	$ 171
2017
Claims Development [Line Items]
Cumulative Incurred Claims and Allocated Claims Adjustment Expenses, net of Reinsurance	3,570	3,475	6,028
Total of IBNR	$ 30
NODs | claim	34
Cumulative Paid Claims and Claims Adjustment Expenses, net of Reinsurance	$ 2,925	1,655	27
2018
Claims Development [Line Items]
Cumulative Incurred Claims and Allocated Claims Adjustment Expenses, net of Reinsurance	5,271	7,779
Total of IBNR	$ 155
NODs | claim	174
Cumulative Paid Claims and Claims Adjustment Expenses, net of Reinsurance	$ 1,981	$ 130
2019
Claims Development [Line Items]
Cumulative Incurred Claims and Allocated Claims Adjustment Expenses, net of Reinsurance	14,391
Total of IBNR	$ 1,097
NODs | claim	1,234
Cumulative Paid Claims and Claims Adjustment Expenses, net of Reinsurance	$ 69

Reserves for Insurance Claims_5

Reserves for Insurance Claims and Claim Expenses - Reconciliation of Disclosure of Incurred and Paid Claims Development to the Liability for Unpaid Claims and Claims Adjustment Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Reinsurance recoverable on unpaid claims	$ 4,939	$ 3,001	$ 1,902	$ 297
Total gross liability for unpaid claims and claim adjustment expenses	23,752	$ 12,811	$ 8,761	$ 3,001
Financial Guarantee Insurance Product Line
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Cumulative Incurred Claims and Allocated Claims Adjustment Expenses, net of Reinsurance	26,064
Cumulative Paid Claims and Claims Adjustment Expenses, net of Reinsurance	7,609
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	18,455
Reinsurance recoverable on unpaid claims	4,939
Unallocated claims adjustment expenses	358
Total gross liability for unpaid claims and claim adjustment expenses	$ 23,752

Reserves for Insurance Claims_6

Reserves for Insurance Claims and Claim Expenses - Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance (Details) - Financial Guarantee Insurance Product Line	Dec. 31, 2019
Average annual percentage payout of incurred claims and allocated claims adjustment expenses by age, net of reinsurance
Year 1	3.00%
Year 2	38.00%
Year 3	91.00%
Year 4	96.00%
Year 5	95.00%
Year 6	100.00%

Earnings per Share (Details)

Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Basic EPS
Net income	$ 50,195	$ 49,763	$ 39,100	$ 32,899	$ 35,520	$ 24,811	$ 25,241	$ 22,355	$ 171,957	$ 107,927	$ 22,050
Basic weighted average shares outstanding (in shares)	68,140	67,849	67,590	66,692	66,308	65,948	65,664	62,099	67,573	65,019	59,816
Basic earnings per share (in dollars per share)	$ 0.74	$ 0.73	$ 0.58	$ 0.49	$ 0.54	$ 0.38	$ 0.38	$ 0.36	$ 2.54	$ 1.66	$ 0.37
Diluted EPS
Net income	$ 50,195	$ 49,763	$ 39,100	$ 32,899	$ 35,520	$ 24,811	$ 25,241	$ 22,355	$ 171,957	$ 107,927	$ 22,050
Gain from change in fair value of warrant liability									0	0	0
Diluted net income									$ 171,957	$ 107,927	$ 22,050
Basic weighted average shares outstanding (in shares)	68,140	67,849	67,590	66,692	66,308	65,948	65,664	62,099	67,573	65,019	59,816
Dilutive effect of issuable shares (in shares)									2,148	2,633	2,370
Diluted weighted average shares outstanding (in shares)	70,276	70,137	69,590	68,996	69,013	68,844	68,616	65,697	69,721	67,652	62,186
Diluted earnings per share (in dollars per share)	$ 0.71	$ 0.69	$ 0.56	$ 0.48	$ 0.46	$ 0.36	$ 0.37	$ 0.34	$ 2.47	$ 1.60	$ 0.35
Antidilutive securities excluded from EPS calculation (in shares)									565	843	995

Warrants (Details)

Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Apr. 30, 2012
Debt Disclosure [Abstract]
Warrants issued (in shares)				992,000
Right to purchase, number of shares per warrant (in shares)				1
Exercise price of warrants (in dollars per warrant)				$ 10
Warrant liability, at fair value	$ 7,641	$ 7,296		$ 5,100
Warrants exercised (in shares)	448,000	151,000	55,000
Stock issued upon exercise of warrants (in shares)	289,000	91,000	32,000
Fair value of warrant liability reclassified to additional paid in capital upon exercise	$ 8,300	$ 1,600
Change in fair value of warrant liability in current period	$ 4,100	$ 400

Share-Based Compensation - Narr

Share-Based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	May 11, 2017	Apr. 16, 2012	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	May 08, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense			$ 13,031	$ 12,557	$ 9,484
Income tax benefit related to share-based compensation			$ 2,700	$ 2,600	$ 2,000
Number of options vested (in shares)			1,300,000
Options exercised (in shares)			1,117,000	803,000	273,000
Aggregate intrinsic value of options exercised			$ 19,400
Weighted average exercise price for options vested (in dollars per share)			$ 11.22
Weighted average remaining contractual term			4 years 9 months 14 days
Options vested aggregate value			$ 29,000
Unrecognized compensation cost related to non-vested stock options			$ 1,100
Employer matching contribution, percent of match (up to)			100.00%
Employer matching contribution, percent of employees' gross pay (up to)			5.00%
Contribution amount			$ 2,500	$ 1,600	$ 1,500
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost, period for recognition			1 year 3 months 22 days
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost, period for recognition			1 year 4 months 24 days
Restricted stock units outstanding (in shares)			1,202,000	1,753,000	2,065,000	2,538,000
Fair value of shares vested			$ 9,400
Weighted average remaining contractual life of RSUs outstanding			1 year 4 months 13 days
Unrecognized compensation cost related to RSUs			$ 7,200	$ 7,800
Restricted Stock Units (RSUs) | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based awards vesting period (in years)			1 year
Restricted Stock Units (RSUs) | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based awards vesting period (in years)			5 years
RSUs Subject to Service Conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units outstanding (in shares)			1,000,000
RSUs Subject to Service and Performance Conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units outstanding (in shares)			200,000
2012 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized to be reserved for issuance (in shares)		5,500,000
2012 Stock Incentive Plan | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized to be reserved for issuance (in shares)		3,850,000
Expiration period (not more than)		10 years	10 years
Award requisite service period		3 years
2012 Stock Incentive Plan | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized to be reserved for issuance (in shares)		1,650,000
2014 Omnibus Incentive Plan | Common Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized to be reserved for issuance (in shares)	6,000,000						4,000,000
Additional shares authorized (in shares)	2,000,000

Share-Based Compensation - Stoc

Share-Based Compensation - Stock Option Activity (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares
Options beginning balance (in shares)	2,882	3,311	3,026
Options granted (in shares)	163	383	574
Options exercised (in shares)	(1,117)	(803)	(273)
Options forfeited (in shares)	0	0	(1)
Options expired (in shares)	0	(9)	(15)
Options ending balance (in shares)	1,928	2,882	3,311
Weighted Average Grant Date Fair Value per Share
Options beginning balance (in dollars per share)	$ 4.24	$ 3.95	$ 3.97
Options granted (in dollars per share)	8.85	6.32	3.89
Options exercised (in dollars per share)	3.88	4.06	3.93
Options forfeited (in dollars per share)	0	0	4.97
Options expired (in dollars per share)	0	4.05	4.76
Options ending balance (in dollars per share)	4.84	4.24	3.95
Weighted Average Exercise Price
Options beginning balance (in dollars per share)	11.42	10.41	10.27
Options granted (in dollars per share)	22.19	18.08	11.06
Options exercised (in dollars per share)	10.19	10.43	10.17
Options forfeited (in dollars per share)	0	0	12.32
Options expired (in dollars per share)	0	10.51	12.02
Options beginning balance (in dollars per share)	$ 13.04	$ 11.42	$ 10.41

Share-Based Compensation - St_2

Share-Based Compensation - Stock Option Valuation Assumptions (Details) - Stock Options	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)	6 years	6 years	6 years
Risk free interest rate, minimum (percent)	2.57%	2.66%	2.04%
Risk free interest rate, maximum (percent)		2.89%	2.08%
Dividend yield (percent)	0.00%	0.00%	0.00%
Expected stock price volatility, minimum (percent)	36.80%	30.10%	30.50%
Expected stock price volatility, maximum (percent)		30.60%	32.70%

Share-Based Compensation - Rest

Share-Based Compensation - Restricted Stock Units Activity (Details) - Restricted Stock Units (RSUs) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares
Non-vested restricted stock units, beginning balance (in shares)	1,753	2,065	2,538
Restricted stock units granted (in shares)	470	701	988
Restricted stock units vested (in shares)	(970)	(913)	(1,367)
Restricted stock units forfeited (in shares)	(51)	(100)	(94)
Non-vested restricted stock units, ending balance (in shares)	1,202	1,753	2,065
Weighted Average Grant Date Fair Value per Share
Non-vested restricted stock units, beginning balance (in dollars per share)	$ 12.06	$ 8.15	$ 6.01
Restricted stock units granted (in dollars per share)	24.42	17.22	11.22
Restricted stock units vested (in dollars per share)	9.71	7.42	6.67
Restricted stock units forfeited (in dollars per share)	15.06	9.89	8.96
Non-vested restricted stock units, ending balance (in dollars per share)	$ 18.67	$ 12.06	$ 8.15

Income Taxes - Components of In

Income Taxes - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Current									$ (386)	$ 1,677	$ 778
Deferred									45,082	26,357	29,964
Total income tax expense	$ 12,594	$ 14,169	$ 11,858	$ 6,075	$ 9,724	$ 7,036	$ 7,098	$ 4,176	$ 44,696	$ 28,034	$ 30,742

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2018	Jan. 01, 2017
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$ 12,594,000	$ 14,169,000	$ 11,858,000	$ 6,075,000	$ 9,724,000	$ 7,036,000	$ 7,098,000	$ 4,176,000	$ 44,696,000	$ 28,034,000	$ 30,742,000
Provisional income tax expense related to Tax Cuts and Jobs Act of 2017											$ 13,600,000
Income Tax Contingency [Line Items]
Purchases of T&L Bonds									7,600,000
Tax and loss bonds	7,600,000								7,600,000
Decrease to retained earnings upon adoption of new accounting standard												$ 0	$ (903,000)
Stranded tax in AOCI related to available-for-sale fixed income holdings												4,200,000
Loss carry forwards subject to expiration	7,300,000								7,300,000
Valuation allowance	7,857,000				8,136,000				7,857,000	8,136,000
Unrecognized tax benefits reserve	0				$ 0				0	$ 0
Annual Limitation Through Year Two
Income Tax Contingency [Line Items]
Loss carry forwards subject to expiration	800,000								800,000
Annual Limitations After Year Two
Income Tax Contingency [Line Items]
Loss carry forwards subject to expiration	300,000								300,000
Domestic Tax Authority | IRS
Income Tax Contingency [Line Items]
Operating loss carryforwards	2,300,000								2,300,000
State and Local Jurisdiction
Income Tax Contingency [Line Items]
Operating loss carryforwards	$ 126,800,000								$ 126,800,000
ASU No. 2018-02
Income Tax Contingency [Line Items]
Decrease to retained earnings upon adoption of new accounting standard												$ 300,000

Income Taxes - Effective Income

Income Taxes - Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21.00%	21.00%	35.00%
State provision	0.50%	0.70%	0.60%
Share-based and other compensation	(1.70%)	(1.40%)	(4.70%)
Warrant gain/loss	0.90%	0.20%	1.80%
Re-measurement from change in federal statutory rate	0.00%	0.00%	25.70%
Other	(0.10%)	0.10%	(0.20%)
Effective income tax rate	20.60%	20.60%	58.20%

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Asset and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax asset
Net operating loss carry forwards	$ 9,244	$ 6,896
Share-based compensation	5,959	6,791
Unearned premium reserve	5,213	5,568
Accrued expenses	4,539	5,495
Capitalized start-up costs	634	727
Deferred ceding commissions	566	821
Unrealized loss on investments	0	2,923
Other	772	364
Total gross deferred tax asset	26,927	29,585
Less: valuation allowance	(7,857)	(8,136)
Total deferred tax asset	19,070	21,449
Deferred tax liability
Contingency reserve	(47,730)	(8,149)
Deferred acquisition costs	(12,902)	(10,145)
Unrealized gain on investments	(7,634)	0
Capitalized software	(5,107)	(4,757)
Intangible assets	(111)	(82)
Other	(1,946)	(1,056)
Net deferred income tax (liability)	(75,430)	(24,189)
Net deferred income tax (liability)	$ 56,360	$ 2,740

Software and Equipment - Net Ba

Software and Equipment - Net Balances (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property plant and equipment	$ 58,956	$ 48,976
Accumulated amortization and depreciation	(32,860)	(24,211)
Software and equipment, net	26,096	24,765
Software
Property, Plant and Equipment [Line Items]
Property plant and equipment	46,522	38,450
Equipment
Property, Plant and Equipment [Line Items]
Property plant and equipment	8,992	7,035
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property plant and equipment	$ 3,442	$ 3,491

Software and Equipment - Narrat

Software and Equipment - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Capitalized costs related to software, equipment, and leaseholds	$ 10.6	$ 9.8	$ 9.1
Depreciation and amortization	$ 9.3	$ 7.8	$ 6.7

Intangible Assets and Goodwil_2

Intangible Assets and Goodwill (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Indefinite-lived Intangible Assets [Line Items]
Goodwill	$ 3,244,000	$ 3,244,000
Total intangible assets and goodwill	3,634,000	3,634,000
Impairment loss related to intangible assets or goodwill	0	0	$ 0
State licenses
Indefinite-lived Intangible Assets [Line Items]
Intangible assets	260,000	260,000
GSE applications
Indefinite-lived Intangible Assets [Line Items]
Intangible assets	$ 130,000	$ 130,000

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)lease_agreement	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Lessee, Lease, Description [Line Items]
Approved insurers, required assets (equal or greater than)	$ 400,000
Approved insurers, risked-based required assets, primary insurance floor	5.60%
Number of operating leases related to corporate headquarters and data center facility | lease_agreement	2
Right-of-use lease assets	$ 6,400
Operating lease liabilities	7,402
Right-of-use assets obtained in exchange for new operating lease liabilities	8,100
Cash paid for amounts included in the measurement of operating lease liabilities	2,500
Operating lease expense	$ 2,200
Rent expense		$ 2,100	$ 1,500
Minimum
Lessee, Lease, Description [Line Items]
Operating lease terms	3 years
Maximum
Lessee, Lease, Description [Line Items]
Operating lease terms	5 years
Corporate Headquarters
Lessee, Lease, Description [Line Items]
Operating lease option to renew, term	5 years

Commitments and Contingencies_2

Commitments and Contingencies - Right-of-Use Asset and Lease Liability Assumptions (Details)	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Weighted-average remaining lease term (in years)	3 years 2 months 12 days
Weighted-average discount rate	6.21%

Commitments and Contingencies_3

Commitments and Contingencies - Future Payment Due Under Operating Leases (Details) $ in Thousands	Dec. 31, 2019USD ($)
Commitments and Contingencies Disclosure [Abstract]
2020	$ 2,537
2021	2,609
2022	2,574
2023	462
Total undiscounted lease payments	8,182
Less effects of discounting	(780)
Present value of lease payments	$ 7,402

Commitments and Contingencies_4

Commitments and Contingencies - Future Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2019USD ($)
Commitments and Contingencies Disclosure [Abstract]
2019	$ 2,346
2020	2,417
2021	2,489
2022	2,564
2023	463
Totals	$ 10,279

Common Stock - Narrative (Detai

Common Stock - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Common stock, outstanding (in shares)		68,358,074	66,318,849
Common stock sold excluding overallotment shares (in shares)	3,700,000
Common stock offered and sold (in shares)	4,300,000
Proceeds from issuance of common stock	$ 79,200	$ 0	$ 79,165	$ 0
Overallotment Option
Class of Stock [Line Items]
Overallotment option included in sale of stock (percent)	15.00%

Regulatory Information - Schedu

Regulatory Information - Schedule of Combined Statutory Net Loss, Statutory Surplus, Contingency Reserve and RTC Ratios (Details) - NMIC and Re One Combined $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Statutory Accounting Practices [Line Items]
Statutory net gain (loss)	$ 15,233	$ (19,784)	$ (35,946)
Statutory surplus	449,602	430,785	371,084
Contingency reserve	$ 531,825	$ 332,702	$ 186,641
Risk-to-capital	15.8	13.1	13.2

Regulatory Information - Narrat

Regulatory Information - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)state	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Statutory Accounting Practices [Line Items]
Maximum permitted RTC ratio	25
Number of states which require minimum amount of statutory capital relative to risk in force | state	16
Mortgage insurance, percentage of indebtedness on single loan	25.00%
Shareholders' equity	$ 930,420	$ 701,500	$ 509,077	$ 475,509
Dividends, restriction with regards to capital surplus	10.00%
Dividends, restriction with regards to capital surplus	$ 16,100
NMIC
Statutory Accounting Practices [Line Items]
Mortgage insurance risk in force	$ 15,400,000	$ 10,000,000
Risk-to-capital	16.3	13.7

Quarterly Financial Data (Una_3

Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Net premiums earned	$ 95,517	$ 92,381	$ 83,249	$ 73,868	$ 69,261	$ 65,407	$ 61,615	$ 54,914	$ 345,015		$ 251,197		$ 165,740
Net investment income	7,962	7,882	7,629	7,383	6,952	6,277	5,735	4,574	30,856		23,538		16,273
Net realized investment (losses) gains	264	81	(113)	(187)	6	(8)	59	0	45		57		208
Other revenues	1,154	1,244	415	42	40	85	44	64	2,855		233		522
Insurance claims and claim expenses	4,269	2,572	2,923	2,743	2,141	1,099	643	1,569	12,507		5,452		5,339
Underwriting and operating expenses	31,296	32,335	32,190	30,800	29,339	30,323	28,958	28,346	126,621	[1]	116,966	[1]	106,362	[1]
Service expenses	937	909	353	49	45	56	62	107	2,248	[1]	270	[1]	617	[1]
Interest expense	2,974	2,979	3,071	3,061	3,028	2,972	5,560	3,419	12,085		14,979		13,528
Loss (gain) from change in fair value of warrant liability	2,632	(1,139)	1,685	5,479	(3,538)	5,464	(109)	(420)	8,657		1,397		4,105
Income before income taxes	62,789	63,932	50,958	38,974	45,244	31,847	32,339	26,531	216,653		135,961		52,792
Income tax expense	12,594	14,169	11,858	6,075	9,724	7,036	7,098	4,176	44,696		28,034		30,742
Net income	$ 50,195	$ 49,763	$ 39,100	$ 32,899	$ 35,520	$ 24,811	$ 25,241	$ 22,355	$ 171,957		$ 107,927		$ 22,050
Income per share
Basic earnings per share (in dollars per share)	$ 0.74	$ 0.73	$ 0.58	$ 0.49	$ 0.54	$ 0.38	$ 0.38	$ 0.36	$ 2.54		$ 1.66		$ 0.37
Diluted earnings per share (in dollars per share)	$ 0.71	$ 0.69	$ 0.56	$ 0.48	$ 0.46	$ 0.36	$ 0.37	$ 0.34	$ 2.47		$ 1.60		$ 0.35
Basic weighted average shares outstanding (in shares)	68,140	67,849	67,590	66,692	66,308	65,948	65,664	62,099	67,573		65,019		59,816
Diluted weighted average shares outstanding (in shares)	70,276	70,137	69,590	68,996	69,013	68,844	68,616	65,697	69,721		67,652		62,186
[1]	Certain "Underwriting and operating expenses" have been reclassified as "Service expenses" in prior periods.

SCHEDULE I - SUMMARY OF INVES_2

SCHEDULE I - SUMMARY OF INVESTMENTS - OTHER THAN INVESTMENTS IN RELATED PARTIES (Details) $ in Thousands	Dec. 31, 2019USD ($)
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost	$ 1,113,779
Fair Value	1,140,940
Amount Reflected on Balance Sheet	1,140,940
U.S. Treasury securities and obligations of U.S. government agencies
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost	48,203
Fair Value	48,929
Amount Reflected on Balance Sheet	48,929
Municipal debt securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost	189,530
Fair Value	190,216
Amount Reflected on Balance Sheet	190,216
Corporate debt securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost	661,719
Fair Value	684,881
Amount Reflected on Balance Sheet	684,881
Asset-backed securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost	170,153
Fair Value	172,642
Amount Reflected on Balance Sheet	172,642
Total bonds
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost	1,069,605
Fair Value	1,096,668
Amount Reflected on Balance Sheet	1,096,668
Short-term investments
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized Cost	44,174
Fair Value	44,272
Amount Reflected on Balance Sheet	$ 44,272

SCHEDULE II - FINANCIAL INFOR_2

SCHEDULE II - FINANCIAL INFORMATION OF REGISTRANT- PARENT COMPANY ONLY - Balance Sheets - Parent Company Only (Details) - USD ($) $ in Thousands		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Apr. 30, 2012
Assets
Fixed maturities, available-for-sale, at fair value (amortized cost of $1,113,779 and $924,987 as of December 31, 2019 and December 31, 2018, respectively)		$ 1,140,940	$ 911,490
Cash and cash equivalents		41,089	25,294	$ 19,196	$ 47,746
Accrued investment income		6,831	5,694
Prepaid expenses		3,512	3,241
Software and equipment, net		26,096	24,765
Other assets		21,171	4,708
Total assets		1,364,818	1,092,043
Liabilities
Term loan		145,764	146,757
Accounts payable and accrued expenses		39,904	31,141
Warrant liability, at fair value		7,641	7,296			$ 5,100
Deferred tax liability, net		56,360	2,740
Other liabilities	[1]	10,025	3,791
Total liabilities		434,398	390,543
Shareholders' equity
Common stock - class A shares, $0.01 par value; 68,358,074 and 66,318,849 shares issued and outstanding as of December 31, 2019 and December 31, 2018, respectively (250,000,000 shares authorized)		684	663
Additional paid-in capital		707,003	682,181
Accumulated other comprehensive income (loss), net of tax		17,288	(14,832)
Retained earnings		205,445	33,488
Total shareholders' equity		930,420	701,500	509,077	475,509
Total liabilities and shareholders' equity		1,364,818	1,092,043
Parent
Assets
Fixed maturities, available-for-sale, at fair value (amortized cost of $1,113,779 and $924,987 as of December 31, 2019 and December 31, 2018, respectively)		41,220	51,957
Cash and cash equivalents		13,431	12,345	$ 528	$ 15,858
Investment in subsidiaries, at equity in net assets		1,025,286	766,193
Accrued investment income		219	216
Prepaid expenses		3,332	3,118
Due from affiliates, net		62,241	41,340
Software and equipment, net		26,096	24,766
Other assets		7,188	1,664
Total assets		1,179,013	901,599
Liabilities
Term loan		145,764	146,757
Accounts payable and accrued expenses		24,871	27,237
Warrant liability, at fair value		7,641	7,296
Deferred tax liability, net		62,921	18,809
Other liabilities		7,396	0
Total liabilities		248,593	200,099
Shareholders' equity
Common stock - class A shares, $0.01 par value; 68,358,074 and 66,318,849 shares issued and outstanding as of December 31, 2019 and December 31, 2018, respectively (250,000,000 shares authorized)		684	663
Additional paid-in capital		707,003	682,181
Accumulated other comprehensive income (loss), net of tax		17,288	(14,832)
Retained earnings		205,445	33,488
Total shareholders' equity		930,420	701,500
Total liabilities and shareholders' equity		$ 1,179,013	$ 901,599
[1]	"Deferred Ceding Commissions" have been reclassified as "Other liabilities" in prior periods.

SCHEDULE II - FINANCIAL INFOR_3

SCHEDULE II - FINANCIAL INFORMATION OF REGISTRANT- PARENT COMPANY ONLY - Balance Sheets Additional Information - Parent Company Only (Details) - $ / shares	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Balance Sheet Statements, Captions [Line Items]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Common stock, issued (in shares)	68,358,074	66,318,849
Common stock, outstanding (in shares)	68,358,074	66,318,849
Common stock, authorized (in shares)	250,000,000	250,000,000
Parent
Condensed Balance Sheet Statements, Captions [Line Items]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, issued (in shares)	68,358,074	68,358,074
Common stock, outstanding (in shares)	66,318,849	66,318,849
Common stock, authorized (in shares)	250,000,000	250,000,000

SCHEDULE II - FINANCIAL INFOR_4

SCHEDULE II - FINANCIAL INFORMATION OF REGISTRANT- PARENT COMPANY ONLY - Statement of Operations - Parent Company Only (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues
Net investment income	$ 7,962	$ 7,882	$ 7,629	$ 7,383	$ 6,952	$ 6,277	$ 5,735	$ 4,574	$ 30,856	$ 23,538	$ 16,273
Net realized investment gains	264	81	(113)	(187)	6	(8)	59	0	45	57	208
Total revenues									378,771	275,025	182,743
Expenses
Interest expense	2,974	2,979	3,071	3,061	3,028	2,972	5,560	3,419	12,085	14,979	13,528
Loss from change in fair value of warrant liability	2,632	(1,139)	1,685	5,479	(3,538)	5,464	(109)	(420)	8,657	1,397	4,105
Total expenses									162,118	139,064	129,951
Income before income taxes	62,789	63,932	50,958	38,974	45,244	31,847	32,339	26,531	216,653	135,961	52,792
Income tax expense	12,594	14,169	11,858	6,075	9,724	7,036	7,098	4,176	44,696	28,034	30,742
Net income	$ 50,195	$ 49,763	$ 39,100	$ 32,899	$ 35,520	$ 24,811	$ 25,241	$ 22,355	171,957	107,927	22,050
Other comprehensive (loss) income, net of tax:
Unrealized gains (losses) in accumulated other comprehensive loss, net of tax expense (benefit) of $82, ($34), and ($49) for each of the years in the three-year period ended December 31, 2019, respectively									32,155	(12,357)	2,559
Reclassification adjustment for losses (gains) included in net loss, net of tax (benefit) expense of $0, ($1) and $0 for each of the years in the three-year period ended December 31, 2019, respectively									(35)	102	(131)
Other comprehensive income (loss), net of tax									32,120	(12,255)	2,428
Comprehensive income									204,077	95,672	24,478
Parent
Revenues
Net investment income									1,124	1,145	691
Net realized investment gains									1	5	1
Total revenues									1,125	1,150	692
Expenses
Other operating expenses									11,714	21,095	16,374
Interest expense									0	2,227	0
Loss from change in fair value of warrant liability									8,657	1,397	4,105
Total expenses									20,371	24,719	20,479
Equity in net income of subsidiaries									226,480	134,127	67,146
Income before income taxes									207,234	110,558	47,359
Income tax expense									35,277	2,631	25,309
Net income									171,957	107,927	22,050
Other comprehensive (loss) income, net of tax:
Unrealized gains (losses) in accumulated other comprehensive loss, net of tax expense (benefit) of $82, ($34), and ($49) for each of the years in the three-year period ended December 31, 2019, respectively									308	(128)	(90)
Reclassification adjustment for losses (gains) included in net loss, net of tax (benefit) expense of $0, ($1) and $0 for each of the years in the three-year period ended December 31, 2019, respectively									0	2	(1)
Equity in other comprehensive income (loss) of subsidiaries									31,812	(12,129)	2,519
Other comprehensive income (loss), net of tax									32,120	(12,255)	2,428
Comprehensive income									$ 204,077	$ 95,672	$ 24,478

SCHEDULE II - FINANCIAL INFOR_5

SCHEDULE II - FINANCIAL INFORMATION OF REGISTRANT- PARENT COMPANY ONLY - Statement of Operations Additional Information - Parent Company Only (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Income Statements, Captions [Line Items]
Change in unrealized investment gains (losses), tax amount	$ 8,548	$ (3,285)	$ 1,234
Reclassification adjustment from AOCI for sale of securities, tax	9	(27)	73
Parent
Condensed Income Statements, Captions [Line Items]
Change in unrealized investment gains (losses), tax amount	82	(34)	(49)
Reclassification adjustment from AOCI for sale of securities, tax	$ 0	$ 1	$ 0

SCHEDULE II - FINANCIAL INFOR_6

SCHEDULE II - FINANCIAL INFORMATION OF REGISTRANT- PARENT COMPANY ONLY - Statements of Cash Flows - Parent Company Only (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	Mar. 31, 2018	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2018	Jan. 01, 2017
Cash flows from operating activities
Net income		$ 50,195	$ 49,763	$ 39,100	$ 32,899	$ 35,520	$ 24,811	$ 25,241	$ 22,355	$ 171,957	$ 107,927	$ 22,050
Adjustments to reconcile net income to net cash provided by operating activities:
Loss from change in fair value of warrant liability										8,657	1,397	4,105
Net realized investment gains										(45)	(57)	(208)
Depreciation and amortization										9,299	7,811	6,663
Amortization of debt discount and debt issuance costs										1,011	3,390	1,473
Deferred income taxes										45,082	25,927	31,102
Share-based compensation expense										13,031	12,557	9,484
Changes in operating assets and liabilities:
Accrued investment income										(1,137)	(1,482)	(791)
Prepaid expenses										(472)	(1,090)	(160)
Other assets										(8,831)	1,304	(1,547)
Accounts payable and accrued expenses										3,888	6,064	(2,486)
Net cash provided by operating activities										208,150	145,861	67,763
Cash flows from investing activities
Purchase of short-term investments										(230,362)	(257,916)	(131,196)
Purchase of fixed-maturity investments, available-for-sale										(290,533)	(356,337)	(219,079)
Proceeds from maturity of short-term investments										244,921	221,685	170,278
Proceeds from redemptions, maturities and sale of fixed-maturity investments, available-for-sale										91,575	179,978	95,435
Software and equipment										(9,956)	(8,060)	(8,510)
Net cash used in investing activities										(194,355)	(220,650)	(93,072)
Cash flows from financing activities
Proceeds from issuance of common stock related to public offering, net of issuance costs	$ 79,200									0	79,165	0
Proceeds from issuance of common stock related to employee equity plans										21,748	12,857	7,103
Proceeds from issuance of common stock related to warrant exercises										0	321	183
Taxes paid related to net share settlement of equity awards										(18,248)	(9,722)	(8,582)
Proceeds from senior note, net										0	149,250	0
Repayments of term loan										(1,500)	(147,375)	(1,500)
Payments of debt issuance/modification costs										0	(3,609)	(445)
Net cash provided by (used in) financing activities										2,000	80,887	(3,241)
Net increase (decrease) in cash, cash equivalents and restricted cash										15,795	6,098	(28,550)
Cash, cash equivalents and restricted cash, beginning of period					25,294				19,196	25,294	19,196	47,746
Cash, cash equivalents and restricted cash, end of period		41,089				25,294				41,089	25,294	19,196
Decrease to retained earnings upon adoption of new accounting standard													$ 0	$ (903)
Parent
Cash flows from operating activities
Net income										171,957	107,927	22,050
Adjustments to reconcile net income to net cash provided by operating activities:
Loss from change in fair value of warrant liability										8,657	1,397	4,105
Net realized investment gains										(1)	(5)	(1)
Depreciation and amortization										286	274	233
Amortization of debt discount and debt issuance costs										1,011	3,390	1,474
Deferred income taxes										44,030	25,163	30,876
Share-based compensation expense										13,031	12,557	9,484
Changes in operating assets and liabilities:
Equity in net income of subsidiaries										(226,480)	(133,837)	(67,239)
Accrued investment income										(3)	(14)	(52)
Receivable from affiliates										(20,902)	(18,932)	(13,103)
Prepaid expenses										(409)	(1,010)	(116)
Other assets										165	1,258	(1,523)
Accounts payable and accrued expenses										(1,640)	5,393	(3,463)
Net cash provided by operating activities										(10,298)	3,561	(17,275)
Cash flows from investing activities
Capitalization of subsidiaries										(800)	(70,500)	(300)
Purchase of short-term investments										(104,192)	(134,376)	(98,255)
Purchase of fixed-maturity investments, available-for-sale										(2,186)	(12,906)	(19,884)
Proceeds from maturity of short-term investments										111,539	122,612	114,170
Proceeds from redemptions, maturities and sale of fixed-maturity investments, available-for-sale										5,877	22,954	11,451
Software and equipment										(854)	(415)	(1,996)
Net cash used in investing activities										9,384	(72,631)	5,186
Cash flows from financing activities
Proceeds from issuance of common stock related to public offering, net of issuance costs										0	79,165	0
Proceeds from issuance of common stock related to employee equity plans										21,748	12,857	7,103
Proceeds from issuance of common stock related to warrant exercises										0	321	183
Taxes paid related to net share settlement of equity awards										(18,248)	(9,722)	(8,582)
Proceeds from senior note, net										0	149,250	0
Repayments of term loan										(1,500)	(147,375)	(1,500)
Payments of debt issuance/modification costs										0	(3,609)	(445)
Net cash provided by (used in) financing activities										2,000	80,887	(3,241)
Net increase (decrease) in cash, cash equivalents and restricted cash										1,086	11,817	(15,330)
Cash, cash equivalents and restricted cash, beginning of period					$ 12,345				$ 528	12,345	528	15,858
Cash, cash equivalents and restricted cash, end of period		$ 13,431				$ 12,345				$ 13,431	$ 12,345	$ 528
ASU No. 2018-02
Cash flows from financing activities
Decrease to retained earnings upon adoption of new accounting standard													$ 300

SCHEDULE II - FINANCIAL INFOR_7

SCHEDULE II - FINANCIAL INFORMATION OF REGISTRANT- PARENT COMPANY ONLY - Supplemental Notes - Parent Company Only (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Dividends, restriction with regards to capital surplus	10.00%
Dividends, restriction with regards to capital surplus	$ 16.1
Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Restricted net assets less aggregate dividend capacity	1,000	$ 800
Operating underwriting and operating expenses	$ 117.1	$ 111.6	$ 101

SCHEDULE IV - FINANCIAL INFOR_2

SCHEDULE IV - FINANCIAL INFORMATION OF REGISTRANT REINSURANCE (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount									$ 398,303	$ 292,064	$ 192,326
Ceded to Other Companies									53,288	40,867	26,586
Net premiums earned	$ 95,517	$ 92,381	$ 83,249	$ 73,868	$ 69,261	$ 65,407	$ 61,615	$ 54,914	345,015	251,197	165,740
Parent
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount									398,303	292,064	192,326	$ 115,830
Ceded to Other Companies									53,288	40,867	26,586	5,349
Assumed from Other Companies									0	0	0	0
Net premiums earned									$ 345,015	$ 251,197	$ 165,740	$ 110,481
Percentage of Amount Assumed to Net									0.00%	0.00%	0.00%	0.00%

Uncategorized Items - nmih20191

Label	Element	Value
Additional Paid-in Capital [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 388,000
AOCI Attributable to Parent [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	282,000
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(282,000)
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 515,000