NMI (NMIH) 10-Q 5 Nov 20 2020 Q3 Quarterly report Financial data

COVER PAGE

COVER PAGE - shares	9 Months Ended
	Sep. 30, 2020	Nov. 03, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
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, par value $0.01
Trading Symbol	NMIH
Security Exchange Name	NASDAQ
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 Common Stock, Shares Outstanding		84,813,362
Entity Central Index Key	0001547903
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands		Sep. 30, 2020	Dec. 31, 2019
Assets
Fixed maturities, available-for-sale, at fair value (amortized cost of $1,624,970 and $1,113,779 as of September 30, 2020 and December 31, 2019, respectively)		$ 1,689,815	$ 1,140,940
Cash and cash equivalents (including restricted cash of $5,555 and $2,662 as of September 30, 2020 and December 31, 2019, respectively)		194,199	41,089
Premiums receivable		48,159	46,085
Accrued investment income		9,766	6,831
Prepaid expenses		4,579	3,512
Deferred policy acquisition costs, net		63,194	59,972
Software and equipment, net		28,131	26,096
Intangible assets and goodwill		3,634	3,634
Prepaid reinsurance premiums		8,014	15,488
Reinsurance recoverable	[1]	17,180	4,939
Other assets	[1]	15,149	16,232
Total assets		2,081,820	1,364,818	[1]
Liabilities
Debt		392,987	145,764
Unearned premiums		116,008	136,642
Accounts payable and accrued expenses		59,316	39,904
Reserve for insurance claims and claim expenses		87,230	23,752
Reinsurance funds withheld		10,364	14,310
Warrant liability, at fair value		3,135	7,641
Deferred tax liability, net		97,451	56,360
Other liabilities		7,773	10,025
Total liabilities		774,264	434,398
Commitments and contingencies
Shareholders' equity
Common stock - class A shares, $0.01 par value; 84,808,516 and 68,358,074 shares issued and outstanding as of September 30, 2020 and December 31, 2019, respectively (250,000,000 shares authorized)		848	684
Additional paid-in capital		930,906	707,003
Accumulated other comprehensive income, net of tax		47,059	17,288
Retained earnings		328,743	205,445
Total shareholders' equity		1,307,556	930,420
Total liabilities and shareholders' equity		$ 2,081,820	$ 1,364,818
[1]	Reinsurance recoverable has been reclassified from "Other assets" in the prior period.

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Fixed maturities, available-for-sale, amortized cost	$ 1,624,970	$ 1,113,779
Restricted cash	$ 5,555	$ 2,662
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, issued (in shares)	84,808,516	68,358,074
Common stock, outstanding (in shares)	84,808,516	68,358,074
Common stock, authorized (in shares)	250,000,000	250,000,000

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenues
Net premiums earned		$ 98,802	$ 92,381	$ 296,463	$ 249,499
Net investment income		8,337	7,882	23,511	22,894
Net realized investment (losses) gains		(4)	81	635	(219)
Other revenues		648	1,244	2,771	1,700
Total revenues		107,783	101,588	323,380	273,874
Expenses
Insurance claims and claim expenses		15,667	2,572	55,698	8,238
Underwriting and operating expenses	[1]	33,969	32,335	96,616	95,325
Service expenses	[1]	557	909	2,381	1,311
Interest expense		7,796	2,979	16,481	9,111
Loss (gain) from change in fair value of warrant liability		437	(1,139)	(4,286)	6,025
Total expenses		58,426	37,656	166,890	120,010
Income before income taxes		49,357	63,932	156,490	153,864
Income tax expense		11,178	14,169	33,192	32,102
Net income		$ 38,179	$ 49,763	$ 123,298	$ 121,762
Earnings per share
Basic (in dollars per share)		$ 0.45	$ 0.73	$ 1.63	$ 1.81
Diluted (in dollars per share)		$ 0.45	$ 0.69	$ 1.55	$ 1.75
Weighted average common shares outstanding
Basic (in shares)		84,805	67,849	75,695	67,381
Diluted (in shares)		85,599	70,137	76,867	69,520
Comprehensive income:
Net income		$ 38,179	$ 49,763	$ 123,298	$ 121,762
Other comprehensive income, net of tax:
Unrealized gains in accumulated other comprehensive income, net of tax expense of $2,494 and $1,376 for the three months ended September 30, 2020 and 2019, respectively, and $7,655 and $8,991 for the nine months ended September 30, 2020 and 2019, respectively		9,381	5,177	28,799	33,824
Reclassification adjustment for realized losses (gains) included in net income, net of tax (benefit) expense of ($1) and $17 for the three months ended September 30, 2020 and 2019, respectively, and ($258) and ($46) for the nine months ended September 30, 2020 and 2019, respectively		3	(64)	972	173
Other comprehensive income, net of tax		9,384	5,113	29,771	33,997
Comprehensive income		$ 47,563	$ 54,876	$ 153,069	$ 155,759
[1]	Certain "Underwriting and operating expenses" have been reclassified as "Service expenses" in prior periods.

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (UNAUDITED) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Net unrealized (losses) gains in accumulated other comprehensive income, tax (benefit) expense	$ 2,494	$ 1,376	$ 7,655	$ 8,991
Reclassification adjustment for realized losses (gains) included in net income, tax expense (benefit)	$ (1)	$ 17	$ (258)	$ (46)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Common Stock - Class A	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Retained Earnings
Beginning balance at Dec. 31, 2018	$ 701,500	$ 663	$ 682,181	$ (14,832)	$ 33,488
Beginning 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	944		944
Common stock: class A shares issued related to warrant exercises (in shares)		39,195
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes	(1,459)	$ 12	(1,471)
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes (in shares)		1,144,000
Share-based compensation expense	2,981		2,981
Change in unrealized investment gains/losses, net of tax benefit/expense	15,016			15,016
Net income	32,899				32,899
Ending balance at Mar. 31, 2019	751,881	$ 675	684,635	184	66,387
Ending balance (in shares) at Mar. 31, 2019		67,502,000
Beginning balance at Dec. 31, 2018	$ 701,500	$ 663	682,181	(14,832)	33,488
Beginning 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 (in shares)	249,000
Net income	$ 121,762
Ending balance at Sep. 30, 2019	873,487	$ 679	698,393	19,165	155,250
Ending balance (in shares) at Sep. 30, 2019		67,927,000
Beginning balance at Mar. 31, 2019	751,881	$ 675	684,635	184	66,387
Beginning balance (in shares) at Mar. 31, 2019		67,502,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock: class A shares issued related to warrant exercises	3,836	$ 1	3,835
Common stock: class A shares issued related to warrant exercises (in shares)		128,000
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes	219	$ 1	218
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes (in shares)		138,000
Share-based compensation expense	3,475		3,475
Change in unrealized investment gains/losses, net of tax benefit/expense	13,868			13,868
Net income	39,100				39,100
Ending balance at Jun. 30, 2019	812,379	$ 677	692,163	14,052	105,487
Ending balance (in shares) at Jun. 30, 2019		67,768,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock: class A shares issued related to warrant exercises	$ 2,177	$ 1	2,176
Common stock: class A shares issued related to warrant exercises (in shares)	82,000	82,000
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes	$ 656	$ 1	655
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes (in shares)		77,000
Share-based compensation expense	3,399		3,399
Change in unrealized investment gains/losses, net of tax benefit/expense	5,113			5,113
Net income	49,763				49,763
Ending balance at Sep. 30, 2019	873,487	$ 679	698,393	19,165	155,250
Ending balance (in shares) at Sep. 30, 2019		67,927,000
Beginning balance at Dec. 31, 2019	930,420	$ 684	707,003	17,288	205,445
Beginning balance (in shares) at Dec. 31, 2019		68,358,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock: class A shares issued related to warrant exercises	221		221
Common stock: class A shares issued related to warrant exercises (in shares)		6,474
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes	(3,750)	$ 5	(3,755)
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes (in shares)		510,000
Share-based compensation expense	2,552		2,552
Change in unrealized investment gains/losses, net of tax benefit/expense	(12,824)			(12,824)
Net income	58,271				58,271
Ending balance at Mar. 31, 2020	974,890	$ 689	706,021	4,464	263,716
Ending balance (in shares) at Mar. 31, 2020		68,874,000
Beginning balance at Dec. 31, 2019	$ 930,420	$ 684	707,003	17,288	205,445
Beginning balance (in shares) at Dec. 31, 2019		68,358,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock: class A shares issued related to warrant exercises (in shares)	6,000
Net income	$ 123,298
Ending balance at Sep. 30, 2020	1,307,556	$ 848	930,906	47,059	328,743
Ending balance (in shares) at Sep. 30, 2020		84,809,000
Beginning balance at Mar. 31, 2020	974,890	$ 689	706,021	4,464	263,716
Beginning balance (in shares) at Mar. 31, 2020		68,874,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock: class A shares issued related to public offering	219,687	$ 159	219,528
Common stock: class A shares issued related to public offering (in shares)		15,870,000
Common stock: class A shares issued related to warrant exercises (in shares)		61,226
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes	(321)		(321)
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes (in shares)		61,000
Share-based compensation expense	2,722		2,722
Change in unrealized investment gains/losses, net of tax benefit/expense	33,211			33,211
Net income	26,848				26,848
Ending balance at Jun. 30, 2020	1,257,037	$ 848	927,950	37,675	290,564
Ending balance (in shares) at Jun. 30, 2020		84,805,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock: class A shares issued related to warrant exercises (in shares)		3,750
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes	0		0
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes (in shares)		4,000
Share-based compensation expense	2,956		2,956
Change in unrealized investment gains/losses, net of tax benefit/expense	9,384			9,384
Net income	38,179				38,179
Ending balance at Sep. 30, 2020	$ 1,307,556	$ 848	$ 930,906	$ 47,059	$ 328,743
Ending balance (in shares) at Sep. 30, 2020		84,809,000

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (UNAUDITED) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Change in unrealized investment gains/losses, tax expense	$ 2,494	$ 8,829	$ (3,409)	$ 1,359	$ 3,686	$ 3,992
Common stock: class A shares issued related to warrant exercises (in shares)				82,000
Common stock, par value (in dollars per share)	$ 0.01
Common stock
Common stock: class A shares issued related to warrant exercises (in shares)	3,750	61,226	6,474	82,000	128,000	39,195
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01			$ 0.01
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes (in shares)	4,000	61,000	510,000	77,000	138,000	1,144,000

CONDENSED CONSOLIDATED STATEM_5

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities
Net income	$ 123,298	$ 121,762
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized investment (gains) losses	(635)	219
(Gain) loss from change in fair value of warrant liability	(4,286)	6,025
Depreciation and amortization	7,378	6,661
Net amortization of premium on investment securities	2,116	943
Amortization of debt discount and debt issuance costs	3,600	754
Deferred income taxes	33,178	31,991
Share-based compensation expense	8,230	9,855
Changes in operating assets and liabilities:
Premiums receivable	(2,074)	(9,723)
Accrued investment income	(2,935)	(1,191)
Prepaid expenses	(1,067)	(1,472)
Deferred policy acquisition costs, net	(3,222)	(9,802)
Other assets	(81)	(8,428)
Unearned premiums	(20,634)	(13,747)
Reserve for insurance claims and claim expenses	63,478	7,694
Reinsurance recoverable	(12,241)	(1,308)
Reinsurance balances, net	2,857	529
Accounts payable and accrued expenses	18,017	(1,195)
Net cash provided by operating activities	214,977	139,567
Cash flows from investing activities
Purchase of short-term investments	(41,872)	(190,122)
Purchase of fixed-maturity investments, available-for-sale	(902,524)	(186,793)
Proceeds from maturity of short-term investments	85,689	200,105
Proceeds from redemptions, maturities and sale of fixed-maturity investments, available-for-sale	346,931	66,996
Software and equipment	(9,102)	(7,449)
Net cash (used in) investing activities	(520,878)	(117,263)
Cash flows from financing activities
Proceeds from issuance of common stock related to public offering, net of issuance costs	219,687	0
Proceeds from issuance of common stock related to employee equity plans	3,407	13,733
Taxes paid related to net share settlement of equity awards	(7,465)	(14,317)
Proceeds from senior secured notes	400,000	0
Repayments of term loan	(147,750)	(1,125)
Payments of debt issuance costs	(8,868)	0
Net cash provided by (used in) financing activities	459,011	(1,709)
Net increase in cash, cash equivalents and restricted cash	153,110	20,595
Cash, cash equivalents and restricted cash, beginning of period	41,089	25,294
Cash, cash equivalents and restricted cash, end of period	194,199	45,889
Supplemental disclosures of cash flow information
Interest paid	4,286	8,060
Income taxes refunded	$ 76	$ 119

Organization, Basis of Presenta

Organization, Basis of Presentation and Summary of Accounting Principles	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Basis of Presentation and Summary of Accounting Principles	Organization, Basis of Presentation and Summary of Accounting Principles 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 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 unaudited condensed consolidated financial statements, which include the results of NMIH and its wholly-owned subsidiaries, have been prepared in accordance with the instructions to Form 10-Q as prescribed by the SEC for interim reporting and include other information and disclosures required by accounting principles generally accepted in the U.S. (GAAP). Our accounts are maintained in U.S. dollars. These statements should be read in conjunction with our consolidated financial statements and notes thereto for the year ended December 31, 2019, included in our 2019 10-K. All intercompany transactions have been eliminated. 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 current period presentation. The results of operations for the interim period may not be indicative of the results that may be expected for the full year ending December 31, 2020. COVID-19 Developments On January 30, 2020, the World Health Organization (WHO) declared the outbreak of COVID-19 a global health emergency and characterized the outbreak as a global pandemic on March 11, 2020. In an effort to stem contagion and control the COVID-19 pandemic, the population at large has severely curtailed day-to-day activity and local, state and federal regulators have imposed a broad set of restrictions on personal and business conduct nationwide. The COVID-19 pandemic, along with the widespread public and regulatory response, has caused a dramatic slowdown in U.S. and global economic activity and a record number of Americans have been furloughed or laid-off. The global dislocation caused by COVID-19 is unprecedented and, while there is broad hope for medical advances that might relieve the crisis and provide for a near-term return to normalized activity, it is not known how long the dislocation will persist and if or when any such medical advances may be developed or made available. In response to the COVID-19 outbreak and continuing uncertainties, we activated our business continuity program to ensure our employees are safe and able to continue serving our customers and their borrowers without interruption. We have also sought to broadly assess the impact that the COVID-19 outbreak has had and may continue to have on the U.S economy and housing market, and the implications for the mortgage insurance market, and our business performance and financial position, including our new business production, default and claims experience, and investment portfolio results. Given the uncertainty that remains, we cannot fully assess or estimate the ultimate impact of COVID-19. Significant Accounting Principles There have been no changes to our significant accounting principles as described in Item 8, " Financial Statements and Supplementary Data - Notes to Consolidated Financial Statements - Note 2 - Summary of Accounting Principles " of our 2019 10-K, other than as noted in " Investments, " " Premium Receivables, " " Reinsurance " and " Recent Accounting Pronouncements - Adopted " below. Investments We hold all investments on an available-for-sale basis and evaluate each position quarterly for impairment. We recognize an impairment on a security through the statement of operations if (i) we intend to sell the impaired security; or (ii) it is more likely than not that we will be required to sell the impaired security prior to recovery of its amortized cost basis. If a sale is intended or likely to be required, we write down the amortized cost basis of the security to fair value and recognize the full amount of the impairment through the statement of operations as a " Realized Investment Loss ." For securities in an unrealized loss position where a sale is not intended or likely to be required, we further assess if the decline in fair value below amortized cost is driven by a credit related impairment, considering several items including, but not limited to: • the severity 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 rating downgrades of the applicable security or issuer by one or more nationally recognized statistical ratings organization; and • other adverse conditions related to or impacting the security or issuer. To the extent we determine that a security impairment is credit-related, an impairment loss is recognized through the statement of operations as a provision for credit loss expense, and presented as a "Realized Investment Loss." We recognize an allowance for credit losses for the difference between the amortized cost and present value of future expected cash flows, limited by the amount the fair value of the security is below its amortized cost. Subsequent changes (favorable and unfavorable) in credit losses are recognized through the statement of operations as a provision for or a reversal of credit loss expense, and presented as a "Realized Investment Gain or Loss." The portion of a security impairment attributed to other non-credit related factors is recognized in other comprehensive income, net of taxes. We have elected to present accrued interest receivable separately from available for sale securities on our consolidated balance sheet. Accrued interest receivable was $9.8 million as of September 30, 2020 and is included in " Accrued Investment Income. " We have elected not to measure an allowance for credit losses for accrued interest receivable on available for sale securities. Accrued interest for available for sale securities is written off against interest income when the receivable has aged 90 days past due. We did not write off any accrued interest receivable during the three or nine months ended September 30, 2020. Premiums Receivable Premiums receivable consists of premiums due on our mortgage insurance policies. If a mortgage insurance premium is unpaid for more than 120 days, the associated receivable is written off against earned premium and the related insurance policy is canceled. We recognize an allowance for credit losses for premiums receivable based on credit losses expected to arise over the life of the receivable. Due to the nature of our insurance policies (a necessary precondition for access to mortgage credit for covered borrowers) and the short duration of the related receivables, we do not typically experience credit losses against our premium receivables and did not establish an allowance for credit loss at September 30, 2020. Premiums receivable may be written off prior to 120 days in the ordinary course of business for non-credit events including, but not limited to, the modification or refinancing of an underlying insured loan. We have established a reserve for premium write-offs based on historical experience; such reserve was deemed to be immaterial at September 30, 2020. Reinsurance We account for premiums, claims and claim expenses that are ceded to reinsurers on a basis consistent 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 has entered into quota share reinsurance treaties effective September 1, 2016 (the 2016 QSR Transaction) , January 1, 2018 (the 2018 QSR Transaction) and April 1, 2020 (the 2020 QSR Transaction) , which we refer to collectively as the QSR Transactions. W e earn profit and ceding commissions in connection with the QSR Transactions. 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 increases 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 and 2020 QSR Transactions, 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 " on the consolidated balance sheets and such ceded claims as reductions to claims expenses on the consolidated statements of operations. As of September 30, 2020, we had $17.2 million of reinsurance recoverables under the QSR Transaction s. We remain directly liable for all claim payments if we are unable to collect the recoverables due from our reinsurers and, as such, we actively monitor and manage our counterparty credit exposure to our reinsurance providers. We establish an allowance for expected credit loss against our reinsurance recoverables if we do not expect to recover amounts due from one or more of our reinsurance counterparties, and report our reinsurance recoverables net of such allowance, if any. We actively monitor the counterparty credit profiles of our reinsurers and each is required to partially collateralize its obligations under the terms of our QSR Transactions. As of September 30, 2020, we did not recognize any allowance for credit loss with respect to our reinsurance recoverables. Variable Interest Entities NMIC is a party to reinsurance agreements with Oaktown Re Ltd., Oaktown Re II Ltd., Oaktown Re III Ltd. and Oaktown Re IV Ltd. (special purpose reinsurance entities collectively referred to as the Oaktown Re Vehicles) effective May 2, 2017, July 25, 2018, July 30, 2019 and July 30, 2020, respectively. At inception of the respective reinsurance agreements, we determined that each of the Oaktown Re Vehicles 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 - Adopted In June 2016, the Financial Accounting Standard Board (FASB) issued Accounting Standards Update (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, C odification 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 shifts 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 are recorded through an allowance for credit losses, rather than a write-down of the asset as was 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 2018-13, 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. Recent Accounting Pronouncements - Not Yet Adopted 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 2019-09 in November 2019, which 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 December 2019, the FASB issued ASU 2019-12, Simplifying the Accounting for 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 will adopt these updates on January 1, 2021 and do not expect them to have material impacts on our consolidated financial statements. In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848) . This update provides optional guidance to ease the potential burden in accounting for reference rate reform on financial reporting. Reference rate reform refers to the global transition away from referencing the London Interbank Offered Rate (LIBOR) in financial contracts, which is expected to be discontinued in 2021. The ASU includes optional expedients and exceptions for applying GAAP to contracts, hedging relationships and other transactions affected by reference rate reform if certain criteria are met. The standard is effective immediately through December 31, 2022 for all entities that have contracts, hedging relationships, and other transactions that reference LIBOR or another reference rate expected to be discontinued because of reference rate reform. We are currently evaluating the impact the adoption of this ASU would have, if any, to our contract modifications that are affected by the discontinuation of LIBOR. In August 2020, the FASB issued ASU 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging— Contracts in Entity's Own Equity (Subtopic 815-40)

Investments

Investments	9 Months Ended
	Sep. 30, 2020
Investments, Debt and Equity Securities [Abstract]
Investments	Investments We hold all investments on an available-for-sale basis and evaluate each position quarterly for impairment. We recognize an impairment on a security through the statement of operations if (i) we intend to sell the impaired security; or (ii) it is more likely than not that we will be required to sell the impaired security prior to recovery of its amortized cost basis. If a sale is intended or likely to be required, we write down the amortized cost basis of the security to fair value and recognize the full amount of the impairment through the statement of operations as a " Realized Investment Loss ." To the extent we determine that a security impairment is credit-related, an impairment loss is recognized through the statement of operations as a provision for credit loss expense. The portion of a security impairment attributed to other non-credit related factors is recognized in other comprehensive income, net of taxes. Fair Values and Gross Unrealized Gains and Losses on Investments Amortized Gross Unrealized Fair Gains Losses As of September 30, 2020 (In Thousands) U.S. Treasury securities and obligations of U.S. government agencies $ 31,204 $ 2,393 $ — $ 33,597 Municipal debt securities 318,436 11,139 (24) 329,551 Corporate debt securities 1,144,217 49,583 (703) 1,193,097 Asset-backed securities 130,757 2,486 (29) 133,214 Total bonds 1,624,614 65,601 (756) 1,689,459 Short-term investments 356 — — 356 Total investments $ 1,624,970 $ 65,601 $ (756) $ 1,689,815 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 We did not own any mortgage-backed securities in our asset-backed securities portfolio at September 30, 2020 o r December 31, 2019. We periodically recognize unsettled trades payable or receivable in connection with our investing activity. Unsettled trades payable represent funds due for investments purchased at period end. Unsettled trades receivable represent funds due for investments sold at period end. The following table presents a breakdown of the fair value of our corporate debt securities by issuer industry group as of September 30, 2020 and December 31, 2019: September 30, 2020 December 31, 2019 Financial 36 % 38 % Consumer 24 26 Utilities 11 9 Communications 11 10 Technology 10 7 Industrial 8 8 Energy — 2 Total 100 % 100 % As of September 30, 2020 and December 31, 2019, approximately $5.7 million and $5.5 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 value of available-for-sale securities as of September 30, 2020 and December 31, 2019, 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 September 30, 2020 Amortized Fair (In Thousands) Due in one year or less $ 79,742 $ 80,330 Due after one through five years 479,455 504,960 Due after five through ten years 912,664 947,919 Due after ten years 22,352 23,392 Asset-backed securities 130,757 133,214 Total investments $ 1,624,970 $ 1,689,815 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 Aging of Unrealized Losses As of September 30, 2020, the investment portfolio had gross unrealized losses of $0.8 million, of which $28 thousand had been in an unrealized loss position for a period of 12 months or longer. For those securities in an unrealized loss position, the length of time 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 September 30, 2020 (Dollars in Thousands) Municipal debt securities 9 $ 15,706 $ (24) — $ — $ — 9 $ 15,706 $ (24) Corporate debt securities 20 101,088 (702) 1 33 (1) 21 101,121 (703) Asset-backed securities 2 7,311 (2) 1 2,724 (27) 3 10,035 (29) Total 31 $ 124,105 $ (728) 2 $ 2,757 $ (28) 33 $ 126,862 $ (756) 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) Allowance for credit losses As of September 30, 2020, we did not recognize an allowance for credit loss for any security in the investment portfolio and we did not record any provision for credit loss for investment securities during the three and nine months ended September 30, 2020. Based on current facts and circumstances, we believe the unrealized losses as of September 30, 2020 are not indicative of the ultimate collectability of the current amortized cost of the securities. During the nine months ended September 30, 2019, we recognized $0.4 million other-than-temporarily impaired (OTTI) losses in connection with the planned sale of a security that was disposed of in April 2019. Net Investment Income The following table presents the components of net investment income: For the three months ended September 30, For the nine months ended September 30, 2020 2019 2020 2019 (In Thousands) Investment income $ 8,624 $ 8,003 $ 24,293 $ 23,240 Investment expenses (287) (121) (782) (346) Net investment income $ 8,337 $ 7,882 $ 23,511 $ 22,894 The following table presents the components of net realized investment gains (losses): For the three months ended September 30, For the nine months ended September 30, 2020 2019 2020 2019 (In Thousands) Gross realized investment gains $ — $ 81 $ 5,126 $ 297 Gross realized investment losses (4) — (4,491) (516) Net realized investment (losses) gains $ (4) $ 81 $ 635 $ (219)

Fair Value of Financial Instrum

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2020
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 September 30, 2020 (In Thousands) U.S. Treasury securities and obligations of U.S. government agencies $ 33,597 $ — $ — $ 33,597 Municipal debt securities — 329,551 — 329,551 Corporate debt securities — 1,193,097 — 1,193,097 Asset-backed securities — 133,214 — 133,214 Cash, cash equivalents and short-term investments 194,555 — — 194,555 Total assets $ 228,152 $ 1,655,862 $ — $ 1,884,014 Warrant liability — — 3,135 3,135 Total liabilities $ — $ — $ 3,135 $ 3,135 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 There were no transfers between Level 2 and Level 3 of the fair value hierarchy during the nine months ended September 30, 2020, or the year ended December 31, 2019. The following is a roll-forward of Level 3 liabilities measured at fair value: For the nine months ended September 30, Warrant Liability 2020 2019 (In Thousands) Balance, January 1 $ 7,641 $ 7,296 Change in fair value of warrant liability included in earnings (4,286) 6,025 Issuance of common stock on warrant exercise (220) (6,957) Balance, September 30 $ 3,135 $ 6,364 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 September 30, 2020 2019 Common stock price $ 17.80 $ 26.26 Risk free interest rate 0.13 % 1.76% Expected life 1.56 years 0.92 years Expected volatility 75.3 % 33.5% Dividend yield 0 % 0 % The changes in fair value of the warrant liability for the nine months ended September 30, 2020 and 2019 are primarily attributable to changes in the price of our common stock during the respective periods, with additional impact related to changes in other Black-Scholes model inputs. The change in fair value of the warrant liability for the nine months ended September 30, 2019 also reflects the impact of the exercises of outstanding warrants. Financial Instruments not Measured at Fair Value On June 19, 2020, we issued $400 million aggregate principal amount of senior secured notes that mature on June 1, 2025 (the Notes). At September 30, 2020, the Notes were carried at a cost of $393.0 million, net of unamortized debt issuance costs of $7.0 million, and had a fair value of $427.5 million as assessed under our Level 2 hierarchy. At December 31, 2019, our 2018 Term Loan was carried at a cost of $145.8 million, net of unamortized debt issuance costs of $2.0 million, and had a fair value of $147.8 million.

Debt

Debt	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Debt	Debt Senior Secured Notes At September 30, 2020, we had $400 million aggregate principal amount of senior secured notes outstanding. The Notes were issued pursuant to an indenture dated June 19, 2020 (the Indenture) and bear interest at a rate of 7.375%, payable semi-annually on June 1 and December 1. A portion of the proceeds from the Notes offering were used to repay the outstanding amount due under our $150 million term loan (2018 Term Loan) and to pay underwriting fees incurred in connection with the offering. Remaining proceeds of $244.4 million are available for general corporate purposes, including to support the growth of our new business production and operations. The Notes mature on June 1, 2025. At any time, or from time to time, prior to March 1, 2025, we may elect to redeem the Notes in whole or in part at a price based on 100% of the aggregate principal amount of any Notes redeemed plus the "Applicable Premium," plus accrued and unpaid interest thereon. Applicable Premium is defined as the greater of (1) 1.0% of the principal amount of the Notes, or (2) the principal value of the Notes plus the present value of all future interest payments. At any time on or after March 1, 2025, we may elect to redeem the Notes in whole or in part at a price equal to 100% of the aggregate principal amount of the Notes to be redeemed plus accrued and unpaid interest thereon. From time to time prior to June 1, 2022, we may also elect to use proceeds raised from one or more equity offerings to redeem up to 40% of the aggregate principal amount of the Notes at a price equal to 107.375% of the aggregate principal amount thereof plus accrued and unpaid interest thereon, subject to certain exceptions. Interest expense for the Notes includes interest and the amortization of capitalized debt issuance costs. In connection with the Notes offering, we recorded capitalized debt issuance costs of $7.4 million. Such amounts will be amortized over the contractual life of the Notes using the effective interest method. At September 30, 2020, $7.0 million of unamortized debt issuance costs remained. Interest expense for the nine months ended September 30, 2020 includes $2.6 million of costs related to the extinguishment of the 2018 Term Loan and issuance of the Notes. We are subject to certain covenants under the Notes (as defined in the Indenture), including, but not limited to, a maximum debt-to-total capitalization ratio of 35%. We were in compliance with all Notes covenants as of September 30, 2020. 2020 Revolving Credit Facility On March 20, 2020, we amended our $85 million three-year secured revolving credit facility (the 2018 Revolving Credit Facility), increasing borrowing capacity under the facility to $100 million, extending its maturity date from May 24, 2021 to February 22, 2023, and reducing the interest cost related to both undrawn commitments and drawn borrowings under the facility (as amended, the 2020 Revolving Credit Facility). Borrowings under the 2020 Revolving Credit Facility may be used for general corporate purposes, including to support the growth of our new business production and operations, and accrue interest at a variable rate equal to, at our discretion, (i) a base rate (as defined in our existing credit agreement (the Credit Agreement), subject to a floor of 1.00% per annum) plus a margin of 0.375% to 1.875% per annum or (ii) the Eurodollar Rate (subject to a floor of —% per annum) plus a margin of 1.375% to 2.875% per annum, based on the applicable corporate credit rating at the time. As of September 30, 2020, no borrowings were drawn under the 2020 Revolving Credit Facility. Under the 2020 Revolving Credit Facility, we are required to pay a quarterly commitment fee on the average daily undrawn amount of 0.175% to 0.525%, based on the applicable corporate credit rating at the time. As of September 30, 2020, the applicable commitment fee was 0.35%. For the three and nine months ended September 30, 2020, we recorded $0.1 million and $0.3 million of commitment fees in interest expense, respectively. We incurred debt issuance costs of $0.8 million in connection with the 2020 Revolving Credit Facility and had $0.6 million of unamortized debt issuance costs associated with the 2018 Revolving Credit Facility remaining at the time of its amendment and replacement. Combined unamortized debt issuance will be amortized through interest expense on a straight-line basis over the contractual life of the 2020 Revolving Credit Facility. At September 30, 2020, remaining unamortized deferred debt issuance costs were $1.1 million. We are subject to certain covenants under the 2020 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 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 at September 30, 2020.

Reinsurance

Reinsurance	9 Months Ended
	Sep. 30, 2020
Reinsurance Disclosures [Abstract]
Reinsurance	ReinsuranceWe enter into third-party reinsurance transactions to actively manage our risk, ensure compliance with PMIERs, state regulatory and other applicable capital requirements (respectively, as defined therein), and support the growth of our business. The Wisconsin Office of the Commissioner of Insurance (Wisconsin OCI) has approved and the GSEs have indicated their non-objection to 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 three months ended For the nine months ended September 30, 2020 September 30, 2019 September 30, 2020 September 30, 2019 (In Thousands) Net premiums written Direct $ 119,323 $ 100,475 $ 331,254 $ 274,418 Ceded (1) (17,501) (11,796) (47,952) (31,207) Net premiums written $ 101,822 $ 88,679 $ 283,302 $ 243,211 Net premiums earned Direct $ 118,552 $ 106,687 $ 351,889 $ 288,165 Ceded (1) (19,750) (14,306) (55,426) (38,666) Net premiums earned $ 98,802 $ 92,381 $ 296,463 $ 249,499 (1) Net of profit commission. Excess-of-loss reinsurance NMIC entered into excess-of-loss reinsurance agreements with the Oaktown Re Vehicles. 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. 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., Oaktown Re III Ltd. and Oaktown IV Ltd.). NMIC ceded aggregate premiums to the Oaktown Re Vehicles of $6.3 million and $13.4 million during the three and nine months ended September 30, 2020 and $4.4 million and $10.3 million during the three and nine months ended September 30, 2019, 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 three and nine months ended September 30, 2020 and 2019, 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 ten The respective reinsurance coverage amounts provided by the Oaktown Re Vehicles decrease from the inception of each agreement over a ten The following table presents the inception date, covered production p eriod, initial and current reinsurance coverage amount, and initial and current first layer retained aggregate loss under each of the ILN Transactions. Current amounts are presented as of September 30, 2020. ( $ values in thousands) Inception Date Covered Production Initial Reinsurance Coverage Current Reinsurance Coverage Initial First Layer Retained Loss Current First Layer Retained Loss (1) 2017 ILN Transaction May 2, 2017 1/1/2013 - 12/31/2016 $ 211,320 $ 40,226 $ 126,793 $ 121,602 2018 ILN Transaction July 25, 2018 1/1/2017 - 5/31/2018 264,545 158,489 125,312 123,354 2019 ILN Transaction July 30, 2019 6/1/2018 - 6/30/2019 326,905 231,877 123,424 123,072 2020-1 ILN Transaction July 30, 2020 7/1/2019 - 3/31/2020 322,076 322,076 169,514 169,514 (1) NMIC applies claims paid on covered policies against its first layer aggregate retained loss exposure and cedes reserves for incurred claims and claims expenses to each applicable ILN Transaction and recognizes a reinsurance recoverable if such incurred claims and claims expenses exceed its current first layer retained loss. 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, 2019 and 2020-1 ILN Transactions, 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 $5.6 million as of September 30, 2020. We are not required to deposit additional funds into the premium deposit accounts in the future and the restricted balances required under these transactions. Quota share reinsurance NMIC is a party to three outstanding quota share reinsurance treaties – the 2016 QSR Transaction, effective September 1, 2016, the 2018 QSR Transaction, effective January 1, 2018 and the 2020 QSR Transaction, effective April 1, 2020. 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 terms of 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 re-assuming the related risk. Under the terms of 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 re-assuming the related risk. Under the terms of the 2020 QSR Transaction, NMIC cedes premiums earned related to 21% of the risk on eligible policies written from April 1, 2020 to December 31, 2020. The 2020 QSR Transaction is scheduled to terminate on December 31, 2030. NMIC has the option, based on certain conditions and subject to a termination fee, to terminate the agreement as of December 31, 2023, or at the end of any calendar quarter thereafter, which would result in NMIC re-assuming the related risk. NMIC may terminate any or all 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 risk-in-force (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 amounts related to the QSR Transactions: For the three months ended For the nine months ended September 30, 2020 September 30, 2019 September 30, 2020 September 30, 2019 (In Thousands) Ceded risk-in-force $ 5,159,061 $ 4,901,809 $ 5,159,061 $ 4,901,809 Ceded premiums earned (24,517) (23,151) (70,738) (65,538) Ceded claims and claim expenses 3,200 766 13,401 2,435 Ceding commission earned 4,798 4,584 13,739 12,961 Profit commission 11,034 13,254 28,718 37,199 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 and 2020 QSR Transactions, 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, 2018 QSR Transaction and 2020 QSR Transaction, generally remain below 60%, 61% and 50%, 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 the 2016 QSR Transaction was $4.8 million as of September 30, 2020. In accordance with the terms of the 2018 and 2020 QSR Transactions, 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 recognized 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 the 2018 QSR Transaction was $12.2 million as of September 30, 2020. The reinsurance recoverable on loss reserves related to the 2020 QSR Transaction was $0.2 million as of September 30, 2020.

Reserves for Insurance Claims a

Reserves for Insurance Claims and Claim Expenses	9 Months Ended
	Sep. 30, 2020
Insurance [Abstract]
Reserves for Insurance Claims and Claim Expenses	Reserves for Insurance Claims and Claim Expenses We hold gross reserves in an amount equal to the estimated liability for insurance claims and claim expenses related to defaults on insured mortgage loans. A loan is considered to be in "default" as of the payment date at which a borrower has missed the preceding two or more consecutive monthly payments. We establish reserves for loans that have been reported to us in default by servicers, referred to as case reserves, and additional loans that we estimate (based on actuarial review and other factors) to be in default that have not yet been reported to us by servicers, referred to as incurred but not reported (IBNR) reserves. We also establish reserves for claim expenses, which represent the estimated cost of the claim administration process, including legal and other fees, as well as other general expenses of administering the claim settlement process. As of September 30, 2020, we had 13,765 primary loans in default and held gross reserves for insurance claims and claim expenses of $87.2 million. During the nine months ended September 30, 2020, we paid 123 claims totaling $5.6 million, including 117 claims covered under the QSR Transactions representing $1.2 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 September 30, 2020, 277 loans in the pool were in default. These 277 loans represented approximately $23.2 million of RIF. Due to the size of the remaining deductible, our expectation that a limited number of loans in default will progress to a claim and the expected severity on such claim submissions (all loans in the pool have loan-to-value (LTV) ratios under 80%), we did not establish any case or IBNR reserves for pool risk at September 30, 2020. In connection with the settlement of pool claims, we applied $0.9 million to the pool deductible through September 30, 2020. At September 30, 2020, the remaining pool deductible was $9.4 million. We have not paid any pool claims to date. 100% of our pool RIF is reinsured under the 2016 QSR Transaction. We had 13,765 loans in default in our primary insured portfolio as of September 30, 2020, which represented a 3.60% default rate against 381,899 to tal policies in-force. We had 1,230 loans in default in our primary insured portfolio as of September 30, 2019, which represented a 0.35% default rate against 350,395 total policies in-force. The increase in our default population is primarily due to challenges borrowers are facing related to the COVID-19 outbreak and their decision to access the forbearance program for federally backed loans codified under the Coronavirus Aid, Relief, and Economic Security (CARES) Act or similar programs made available by private lenders. The size of the reserve we establish for each defaulted loan (and by extension our aggregate reserve for claims and claim expenses) reflects our best estimate of the future claim payment to be made for each individual loan in default. Our future claims exposure is a function of the number of defaulted loans that progress to claim payment (which we refer to as frequency) and the amount to be paid to settle such claims (which we refer to as severity). Our estimates of claims frequency and severity are not formulaic, rather they are broadly synthesized based on historical observed experience for similarly situated loans and assumptions about future macroeconomic factors. We generally observe that forbearance programs are an effective tool to bridge dislocated borrowers from a time of acute stress to a future date when they can resume timely payment of their mortgage obligations. The effectiveness of forbearance programs is enhanced by the availability of various repayment and loan modification options which allow borrowers to amortize or, in certain instances, outright defer payments otherwise due during the forbearance period over an extended length of time. In response to the COVID-19 outbreak, the Federal Housing Financing Agency (FHFA) and GSEs have introduced new repayment and loan modification options to further assist borrowers with their transition out of forbearance programs and default status. Our reserve setting process considers the beneficial impact of forbearance, foreclosure moratorium and other assistance programs available to defaulted borrowers. At September 30, 2020, we established lower reserves for defaults that we consider to be connected to the COVID-19 outbreak given our expectation that forbearance, repayment and modification, and other assistance programs will aid affected borrowers and drive higher cure rates on such defaults than we would otherwise expect to experience on similarly situated loans that did not benefit from broad-based assistance programs. While we established lower reserves per defaulted loan at September 30, 2020, our total reserve position and claims and claim expenses increased as of and during the period ended September 30, 2020 due to the growth in the size of our default population. The following table provides a reconciliation of the beginning and ending gross reserve balances for primary insurance claims and claim expenses: For the nine months ended September 30, 2020 2019 (In Thousands) Beginning balance $ 23,752 $ 12,811 Less reinsurance recoverables (1) (4,939) (3,001) Beginning balance, net of reinsurance recoverables 18,813 9,810 Add claims incurred: Claims and claim expenses incurred: Current year (2) 61,198 10,948 Prior years (3) (5,500) (2,710) Total claims and claim expenses incurred 55,698 8,238 Less claims paid: Claims and claim expenses paid: Current year (2) 152 — Prior years (3) 4,309 2,401 Reinsurance terminations (4) — (549) Total claims and claim expenses paid 4,461 1,852 Reserve at end of period, net of reinsurance recoverables 70,050 16,196 Add reinsurance recoverables (1) 17,180 4,309 Ending balance $ 87,230 $ 20,505 (1) Related to ceded losses recoverable under the QSR Transactions. See Note 5, " 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 5, "Reinsurance" for additional information. The "claims incurred" section of the table above shows claims and claim expenses incurred on defaults occurring in current and prior years, including IBNR reserves and is presented net of reinsurance. The amount of claims incurred relating to current year defaults represents the estimated amount of claims and claim expenses to ultimately be paid on such loans. We recognized $5.5 million and $2.7 million of favorable prior year development during the nine months ended September 30, 2020 and 2019, respectively, primarily due to the curing of previously reported defaults. We may increase or decrease our claim estimates and reserves as we learn additional information about individual defaulted loans, and continue to observe and analyze

Earnings per Share (EPS)

Earnings per Share (EPS)	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Earnings per Share (EPS)	Earnings per Share (EPS) 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 restricted stock units (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 three months ended September 30, For the nine months ended September 30, 2020 2019 2020 2019 (In Thousands, except for per share data) Net income $ 38,179 $ 49,763 $ 123,298 $ 121,762 Basic weighted average shares outstanding 84,805 67,849 75,695 67,381 Basic earnings per share $ 0.45 $ 0.73 $ 1.63 $ 1.81 Net income $ 38,179 $ 49,763 $ 123,298 $ 121,762 Gain from change in fair value of warrant liability — (1,139) (4,286) — Diluted net income $ 38,179 $ 48,624 $ 119,012 $ 121,762 Basic weighted average shares outstanding 84,805 67,849 75,695 67,381 Dilutive effect of issuable shares 794 2,288 1,172 2,139 Diluted weighted average shares outstanding 85,599 70,137 76,867 69,520 Diluted earnings per share $ 0.45 $ 0.69 $ 1.55 $ 1.75 Anti-dilutive shares 420 6 91 642

Warrants

Warrants	9 Months Ended
	Sep. 30, 2020
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 three months ended September 30, 2020, no warrants were exercised. During the nine months ended September 30, 2020, nine thousand warrants were exercised resulting in the issuance of six thousand shares of common stock. Upon exercise, we reclassified approximately $0.2 million of warrant fair value from warrant liability to additional paid-in capital. During the three months ended September 30, 2019, 130 thousand warrants were exercised resulting in the issuance of 82 thousand shares of common stock. Upon exercise, we reclassified approximately $2.2 million of warrant fair value from warrant liability to additional paid-in capital, of which $0.9 million related to changes in fair value during the three months ended September 30, 2019. During the nine months ended September 30, 2019, 390 thousand warrants were exercised resulting in the issuance of 249 thousand shares of common stock. Upon exercise, we reclassified approximately $7.0 million of warrant fair value from warrant liability to additional paid-in capital, of which $3.2 million related to changes in fair value during the nine months ended September 30, 2019.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income TaxesWe 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. Our effective tax rate on our pre-tax income was 22.6% and 21.2% for the three and nine months ended September 30, 2020, respectively, compared to 22.2% and 20.9% for the three and nine months ended September 30, 2019, respectively. Our provision for income taxes for interim reporting periods is established based on our estimated annual effective tax rate for a given year. Our effective tax rate may fluctuate between interim periods due to the impact of discrete items not included in our estimated annual effective tax rate, including the tax effects associated with the vesting of RSUs and exercise of options, and the change in fair value of our warrant liability. Such items are treated on a discrete basis in the reporting period in which they occur. 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), and only 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, our interim provision for income taxes for the three and nine months ended September 30, 2020 represents a change in our net deferred tax liability. As of September 30, 2020, we held $7.6 million of tax and loss bonds in "Other assets" in our condensed consolidated balance sheet.

Common Stock

Common Stock	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Common Stock	Common Stock As of September 30, 2020, we had 84.8 million outstanding shares of 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 per share on all matters to be voted upon by stockholders, and there are no cumulative voting rights. Holders of common stock are entitled to receive dividends ratably if any are declared. On June 8, 2020, we completed the sale of 13.8 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 15.9 million shares of common stock issued. The common stock offering generated proceeds of $219.7 million, net of underwriting discounts, commissions and other direct offering expenses.

Regulatory Information

Regulatory Information	9 Months Ended
	Sep. 30, 2020
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 income (loss) was as follows: For the three months ended September 30, For the nine months ended September 30, 2020 2019 2020 2019 (In Thousands) Statutory net (loss) gain $ (5,600) $ 8,055 $ (22,614) $ 13,594 The Wisconsin OCI has imposed a prescribed accounting practice for the treatment of statutory contingency reserves that differs from the treatment promulgated by the NAIC. Under Wisconsin OCI's prescribed practice mortgage guaranty insurers are required to reflect changes in their contingency reserves through statutory income. Such treatment contrasts with the NAIC treatment, which records changes to contingency reserves directly to unassigned funds. As a Wisconsin-domiciled insurer, NMIC's statutory net income reflects an expense associated with the change in its contingency reserve. While such treatment impacts NMIC's statutory net income, it does not have an effect on the company's statutory capital position. NMIC and Re One's combined statutory surplus, contingency reserve, statutory capital and risk-to-capital (RTC) ratio were as follows: September 30, 2020 December 31, 2019 (In Thousands) Statutory surplus $ 883,580 $ 449,602 Contingency reserve 707,769 531,825 Statutory capital (1) $ 1,591,349 $ 981,427 RTC ratio 12.5:1 15.8:1 (1) Represents the total of the statutory surplus and contingency reserve. In June 2020, NMIH contributed approximately $445 million of capital to NMIC following completion of its respective Notes and common stock offerings. 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. NMIC and Re One are subject to certain rules and regulations prescribed by jurisdictions in which they are authorized to operate and the GSEs that may restrict their ability to pay dividends to NMIH. Since inception, NMIC and Re One have not paid any dividends to NMIH. NMIC and Re One have the capacity to pay aggregate ordinary dividends as calculated under Wisconsin law of $16.1 million to NMIH during the 12-month period ending December 31, 2020.

Subsequent Event

Subsequent Event	9 Months Ended
	Sep. 30, 2020
Subsequent Events [Abstract]
Subsequent Event	Subsequent Event Excess-of-loss reinsurance On October 29, 2020, NMIC entered into a reinsurance agreement with Oaktown Re V Ltd. (Oaktown Re V), a Bermuda domiciled special purpose reinsurer, that provides for up to $242.4 million of aggregate excess-of-loss reinsurance coverage at inception for new delinquencies on an existing portfolio of mortgage insurance policies primarily written between April 1, 2020 and September 30, 2020. For the reinsurance coverage period, NMIC will retain the first layer of $121.2 million of aggregate losses and Oaktown Re V will then provide second layer coverage up to the outstanding reinsurance coverage amount. NMIC will then retain losses in excess of the outstanding reinsurance coverage amount. Oaktown Re V financed the coverage by issuing mortgage insurance-linked notes in an aggregate principal amount of $242.4 million to unaffiliated investors. The notes issued by Oaktown Re V mature on October 25, 2030; all proceeds raised were deposited into a reinsurance trust to collateralize and fund the obligations of Oaktown Re V to NMIC under the reinsurance agreement. Funds in the reinsurance trust account are required to be invested in high credit quality money market funds at all times. We refer to NMIC's reinsurance agreement with and the insurance-linked notes issued by Oaktown Re V as the 2020-2 ILN Transaction. Under the terms of the 2020-2 ILN Transaction, NMIC makes risk premium payments for the applicable outstanding reinsurance coverage amount and pays Oaktown Re V for anticipated operating expenses (capped at $250,000 per year). 2020 Revolving Credit Facility On October 30, 2020, we entered into a Joinder Agreement, among NMIH, NMIS, JPMorgan Chase Bank, N.A., as administrative Agent and Citibank, N.A., as lender, (the "Joinder") to the Company's existing Credit Agreement, increasing the

Organization, Basis of Presen_2

Organization, Basis of Presentation and Summary of Accounting Principles (Policies)	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements, which include the results of NMIH and its wholly-owned subsidiaries, have been prepared in accordance with the instructions to Form 10-Q as prescribed by the SEC for interim reporting and include other information and disclosures required by accounting principles generally accepted in the U.S. (GAAP). Our accounts are maintained in U.S. dollars. These statements should be read in conjunction with our consolidated financial statements and notes thereto for the year ended December 31, 2019, included in our 2019 10-K. All intercompany transactions have been eliminated. 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 current period presentation. The results of operations for the interim period may not be indicative of the results that may be expected for the full year ending December 31, 2020.
Investments	Investments We hold all investments on an available-for-sale basis and evaluate each position quarterly for impairment. We recognize an impairment on a security through the statement of operations if (i) we intend to sell the impaired security; or (ii) it is more likely than not that we will be required to sell the impaired security prior to recovery of its amortized cost basis. If a sale is intended or likely to be required, we write down the amortized cost basis of the security to fair value and recognize the full amount of the impairment through the statement of operations as a " Realized Investment Loss ." For securities in an unrealized loss position where a sale is not intended or likely to be required, we further assess if the decline in fair value below amortized cost is driven by a credit related impairment, considering several items including, but not limited to: • the severity 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 rating downgrades of the applicable security or issuer by one or more nationally recognized statistical ratings organization; and • other adverse conditions related to or impacting the security or issuer. To the extent we determine that a security impairment is credit-related, an impairment loss is recognized through the statement of operations as a provision for credit loss expense, and presented as a "Realized Investment Loss." We recognize an allowance for credit losses for the difference between the amortized cost and present value of future expected cash flows, limited by the amount the fair value of the security is below its amortized cost. Subsequent changes (favorable and unfavorable) in credit losses are recognized through the statement of operations as a provision for or a reversal of credit loss expense, and presented as a "Realized Investment Gain or Loss." The portion of a security impairment attributed to other non-credit related factors is recognized in other comprehensive income, net of taxes. We have elected to present accrued interest receivable separately from available for sale securities on our consolidated balance sheet. Accrued interest receivable was $9.8 million as of September 30, 2020 and is included in " Accrued Investment Income. " We have elected not to measure an allowance for credit losses for accrued interest receivable on available for sale securities. Accrued interest for available for sale securities is written off against interest income when the receivable has aged 90 days past due. We did not write off any accrued interest receivable during the three or nine months ended September 30, 2020.
Premiums Receivable	Premiums Receivable Premiums receivable consists of premiums due on our mortgage insurance policies. If a mortgage insurance premium is unpaid for more than 120 days, the associated receivable is written off against earned premium and the related insurance policy is canceled. We recognize an allowance for credit losses for premiums receivable based on credit losses expected to arise over the life of the receivable. Due to the nature of our insurance policies (a necessary precondition for access to mortgage credit for covered borrowers) and the short duration of the related receivables, we do not typically experience credit losses against our premium receivables and did not establish an allowance for credit loss at September 30, 2020. Premiums receivable may be written off prior to 120 days in the ordinary course of business for non-credit events including, but not limited to, the modification or refinancing of an underlying insured loan. We have established a reserve for premium write-offs based on historical experience; such reserve was deemed to be immaterial at September 30, 2020.
Reinsurance	Reinsurance We account for premiums, claims and claim expenses that are ceded to reinsurers on a basis consistent 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 has entered into quota share reinsurance treaties effective September 1, 2016 (the 2016 QSR Transaction) , January 1, 2018 (the 2018 QSR Transaction) and April 1, 2020 (the 2020 QSR Transaction) , which we refer to collectively as the QSR Transactions. W e earn profit and ceding commissions in connection with the QSR Transactions. 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 increases 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 and 2020 QSR Transactions, 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 " on the consolidated balance sheets and such ceded claims as reductions to claims expenses on the consolidated statements of operations. As of September 30, 2020, we had $17.2 million of reinsurance recoverables under the QSR Transaction s. We remain directly liable for all claim payments if we are unable to collect the recoverables due from our reinsurers and, as such, we actively monitor and manage our counterparty credit exposure to our reinsurance providers. We establish an allowance for expected credit loss against our reinsurance recoverables if we do not expect to recover amounts due from one or more of our reinsurance counterparties, and report our reinsurance recoverables net of such allowance, if any. We actively monitor the counterparty credit profiles of our reinsurers and each is required to partially collateralize its obligations under the terms of our QSR Transactions. As of September 30, 2020, we did not recognize any allowance for credit loss with respect to our reinsurance recoverables.
Variable Interest Entities	Variable Interest Entities NMIC is a party to reinsurance agreements with Oaktown Re Ltd., Oaktown Re II Ltd., Oaktown Re III Ltd. and Oaktown Re IV Ltd. (special purpose reinsurance entities collectively referred to as the Oaktown Re Vehicles) effective May 2, 2017, July 25, 2018, July 30, 2019 and July 30, 2020, respectively. At inception of the respective reinsurance agreements, we determined that each of the Oaktown Re Vehicles 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 June 2016, the Financial Accounting Standard Board (FASB) issued Accounting Standards Update (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, C odification 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 shifts 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 are recorded through an allowance for credit losses, rather than a write-down of the asset as was 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 2018-13, 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. Recent Accounting Pronouncements - Not Yet Adopted 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 2019-09 in November 2019, which 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 December 2019, the FASB issued ASU 2019-12, Simplifying the Accounting for 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 will adopt these updates on January 1, 2021 and do not expect them to have material impacts on our consolidated financial statements. In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848) . This update provides optional guidance to ease the potential burden in accounting for reference rate reform on financial reporting. Reference rate reform refers to the global transition away from referencing the London Interbank Offered Rate (LIBOR) in financial contracts, which is expected to be discontinued in 2021. The ASU includes optional expedients and exceptions for applying GAAP to contracts, hedging relationships and other transactions affected by reference rate reform if certain criteria are met. The standard is effective immediately through December 31, 2022 for all entities that have contracts, hedging relationships, and other transactions that reference LIBOR or another reference rate expected to be discontinued because of reference rate reform. We are currently evaluating the impact the adoption of this ASU would have, if any, to our contract modifications that are affected by the discontinuation of LIBOR. In August 2020, the FASB issued ASU 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging— Contracts in Entity's Own Equity (Subtopic 815-40) . This update simplifies the accounting for convertible instruments and contracts on an entity's own equity, including warrants, eliminating certain triggers for derivative accounting. The standard will take effect for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2021. Early adoption is permitted, but no earlier than 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, including our warrant liability.
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 restricted stock units (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.

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2020
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 September 30, 2020 (In Thousands) U.S. Treasury securities and obligations of U.S. government agencies $ 31,204 $ 2,393 $ — $ 33,597 Municipal debt securities 318,436 11,139 (24) 329,551 Corporate debt securities 1,144,217 49,583 (703) 1,193,097 Asset-backed securities 130,757 2,486 (29) 133,214 Total bonds 1,624,614 65,601 (756) 1,689,459 Short-term investments 356 — — 356 Total investments $ 1,624,970 $ 65,601 $ (756) $ 1,689,815 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
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 September 30, 2020 and December 31, 2019: September 30, 2020 December 31, 2019 Financial 36 % 38 % Consumer 24 26 Utilities 11 9 Communications 11 10 Technology 10 7 Industrial 8 8 Energy — 2 Total 100 % 100 %
Schedule of investments by maturity	The amortized cost and fair value of available-for-sale securities as of September 30, 2020 and December 31, 2019, 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 September 30, 2020 Amortized Fair (In Thousands) Due in one year or less $ 79,742 $ 80,330 Due after one through five years 479,455 504,960 Due after five through ten years 912,664 947,919 Due after ten years 22,352 23,392 Asset-backed securities 130,757 133,214 Total investments $ 1,624,970 $ 1,689,815 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
Schedule of aging unrealized losses	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 September 30, 2020 (Dollars in Thousands) Municipal debt securities 9 $ 15,706 $ (24) — $ — $ — 9 $ 15,706 $ (24) Corporate debt securities 20 101,088 (702) 1 33 (1) 21 101,121 (703) Asset-backed securities 2 7,311 (2) 1 2,724 (27) 3 10,035 (29) Total 31 $ 124,105 $ (728) 2 $ 2,757 $ (28) 33 $ 126,862 $ (756) 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)
Schedule of components of net investment income	The following table presents the components of net investment income: For the three months ended September 30, For the nine months ended September 30, 2020 2019 2020 2019 (In Thousands) Investment income $ 8,624 $ 8,003 $ 24,293 $ 23,240 Investment expenses (287) (121) (782) (346) Net investment income $ 8,337 $ 7,882 $ 23,511 $ 22,894
Schedule of net realized investment gains (losses)	The following table presents the components of net realized investment gains (losses): For the three months ended September 30, For the nine months ended September 30, 2020 2019 2020 2019 (In Thousands) Gross realized investment gains $ — $ 81 $ 5,126 $ 297 Gross realized investment losses (4) — (4,491) (516) Net realized investment (losses) gains $ (4) $ 81 $ 635 $ (219)

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2020
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 September 30, 2020 (In Thousands) U.S. Treasury securities and obligations of U.S. government agencies $ 33,597 $ — $ — $ 33,597 Municipal debt securities — 329,551 — 329,551 Corporate debt securities — 1,193,097 — 1,193,097 Asset-backed securities — 133,214 — 133,214 Cash, cash equivalents and short-term investments 194,555 — — 194,555 Total assets $ 228,152 $ 1,655,862 $ — $ 1,884,014 Warrant liability — — 3,135 3,135 Total liabilities $ — $ — $ 3,135 $ 3,135 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
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 nine months ended September 30, Warrant Liability 2020 2019 (In Thousands) Balance, January 1 $ 7,641 $ 7,296 Change in fair value of warrant liability included in earnings (4,286) 6,025 Issuance of common stock on warrant exercise (220) (6,957) Balance, September 30 $ 3,135 $ 6,364
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 September 30, 2020 2019 Common stock price $ 17.80 $ 26.26 Risk free interest rate 0.13 % 1.76% Expected life 1.56 years 0.92 years Expected volatility 75.3 % 33.5% Dividend yield 0 % 0 %

Reinsurance (Tables)

Reinsurance (Tables)	9 Months Ended
	Sep. 30, 2020
Reinsurance Disclosures [Abstract]
Schedule of effects of reinsurance	The effect of our reinsurance agreements on premiums written and earned is as follows: For the three months ended For the nine months ended September 30, 2020 September 30, 2019 September 30, 2020 September 30, 2019 (In Thousands) Net premiums written Direct $ 119,323 $ 100,475 $ 331,254 $ 274,418 Ceded (1) (17,501) (11,796) (47,952) (31,207) Net premiums written $ 101,822 $ 88,679 $ 283,302 $ 243,211 Net premiums earned Direct $ 118,552 $ 106,687 $ 351,889 $ 288,165 Ceded (1) (19,750) (14,306) (55,426) (38,666) Net premiums earned $ 98,802 $ 92,381 $ 296,463 $ 249,499 (1) Net of profit commission. The following table shows amounts related to the QSR Transactions: For the three months ended For the nine months ended September 30, 2020 September 30, 2019 September 30, 2020 September 30, 2019 (In Thousands) Ceded risk-in-force $ 5,159,061 $ 4,901,809 $ 5,159,061 $ 4,901,809 Ceded premiums earned (24,517) (23,151) (70,738) (65,538) Ceded claims and claim expenses 3,200 766 13,401 2,435 Ceding commission earned 4,798 4,584 13,739 12,961 Profit commission 11,034 13,254 28,718 37,199
Schedule of ILN transactions	The following table presents the inception date, covered production p eriod, initial and current reinsurance coverage amount, and initial and current first layer retained aggregate loss under each of the ILN Transactions. Current amounts are presented as of September 30, 2020. ( $ values in thousands) Inception Date Covered Production Initial Reinsurance Coverage Current Reinsurance Coverage Initial First Layer Retained Loss Current First Layer Retained Loss (1) 2017 ILN Transaction May 2, 2017 1/1/2013 - 12/31/2016 $ 211,320 $ 40,226 $ 126,793 $ 121,602 2018 ILN Transaction July 25, 2018 1/1/2017 - 5/31/2018 264,545 158,489 125,312 123,354 2019 ILN Transaction July 30, 2019 6/1/2018 - 6/30/2019 326,905 231,877 123,424 123,072 2020-1 ILN Transaction July 30, 2020 7/1/2019 - 3/31/2020 322,076 322,076 169,514 169,514 (1) NMIC applies claims paid on covered policies against its first layer aggregate retained loss exposure and cedes reserves for incurred claims and claims expenses to each applicable ILN Transaction and recognizes a reinsurance recoverable if such incurred claims and claims expenses exceed its current first layer retained loss.

Reserves for Insurance Claims_2

Reserves for Insurance Claims and Claim Expenses (Tables)	9 Months Ended
	Sep. 30, 2020
Insurance [Abstract]
Reconciliation of liability for insurance claims and claim expenses	The following table provides a reconciliation of the beginning and ending gross reserve balances for primary insurance claims and claim expenses: For the nine months ended September 30, 2020 2019 (In Thousands) Beginning balance $ 23,752 $ 12,811 Less reinsurance recoverables (1) (4,939) (3,001) Beginning balance, net of reinsurance recoverables 18,813 9,810 Add claims incurred: Claims and claim expenses incurred: Current year (2) 61,198 10,948 Prior years (3) (5,500) (2,710) Total claims and claim expenses incurred 55,698 8,238 Less claims paid: Claims and claim expenses paid: Current year (2) 152 — Prior years (3) 4,309 2,401 Reinsurance terminations (4) — (549) Total claims and claim expenses paid 4,461 1,852 Reserve at end of period, net of reinsurance recoverables 70,050 16,196 Add reinsurance recoverables (1) 17,180 4,309 Ending balance $ 87,230 $ 20,505 (1) Related to ceded losses recoverable under the QSR Transactions. See Note 5, " 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 5, "Reinsurance" for additional information.

Earnings per Share (EPS) (Table

Earnings per Share (EPS) (Tables)	9 Months Ended
	Sep. 30, 2020
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 three months ended September 30, For the nine months ended September 30, 2020 2019 2020 2019 (In Thousands, except for per share data) Net income $ 38,179 $ 49,763 $ 123,298 $ 121,762 Basic weighted average shares outstanding 84,805 67,849 75,695 67,381 Basic earnings per share $ 0.45 $ 0.73 $ 1.63 $ 1.81 Net income $ 38,179 $ 49,763 $ 123,298 $ 121,762 Gain from change in fair value of warrant liability — (1,139) (4,286) — Diluted net income $ 38,179 $ 48,624 $ 119,012 $ 121,762 Basic weighted average shares outstanding 84,805 67,849 75,695 67,381 Dilutive effect of issuable shares 794 2,288 1,172 2,139 Diluted weighted average shares outstanding 85,599 70,137 76,867 69,520 Diluted earnings per share $ 0.45 $ 0.69 $ 1.55 $ 1.75 Anti-dilutive shares 420 6 91 642

Regulatory Information (Tables)

Regulatory Information (Tables)	9 Months Ended
	Sep. 30, 2020
Insurance [Abstract]
Schedule of statutory net income (loss), surplus, contingency reserve and risk-to-capital ratio	NMIC and Re One's combined statutory net income (loss) was as follows: For the three months ended September 30, For the nine months ended September 30, 2020 2019 2020 2019 (In Thousands) Statutory net (loss) gain $ (5,600) $ 8,055 $ (22,614) $ 13,594 The Wisconsin OCI has imposed a prescribed accounting practice for the treatment of statutory contingency reserves that differs from the treatment promulgated by the NAIC. Under Wisconsin OCI's prescribed practice mortgage guaranty insurers are required to reflect changes in their contingency reserves through statutory income. Such treatment contrasts with the NAIC treatment, which records changes to contingency reserves directly to unassigned funds. As a Wisconsin-domiciled insurer, NMIC's statutory net income reflects an expense associated with the change in its contingency reserve. While such treatment impacts NMIC's statutory net income, it does not have an effect on the company's statutory capital position. NMIC and Re One's combined statutory surplus, contingency reserve, statutory capital and risk-to-capital (RTC) ratio were as follows: September 30, 2020 December 31, 2019 (In Thousands) Statutory surplus $ 883,580 $ 449,602 Contingency reserve 707,769 531,825 Statutory capital (1) $ 1,591,349 $ 981,427 RTC ratio 12.5:1 15.8:1 (1) Represents the total of the statutory surplus and contingency reserve.

Organization, Basis of Presen_3

Organization, Basis of Presentation and Summary of Accounting Principles - Narrative (Details) $ in Thousands	Sep. 30, 2020USD ($)state	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Dec. 31, 2018USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of states in which the entity operates | state	50
Effects of Reinsurance [Line Items]
Accrued interest receivable	$ 9,800
Reinsurance recoverable on loss reserve	17,180	$ 4,939	$ 4,309	$ 3,001
Third-party reinsurers | QSR transactions
Effects of Reinsurance [Line Items]
Reinsurance recoverable on loss reserve	$ 17,200

Investments - Fair Values and G

Investments - Fair Values and Gross Unrealized Gains and Losses (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,624,970	$ 1,113,779
Gross unrealized gains	65,601	28,579
Gross unrealized losses	(756)	(1,418)
Fair Value	1,689,815	1,140,940
U.S. Treasury securities and obligations of U.S. government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	31,204	48,203
Gross unrealized gains	2,393	784
Gross unrealized losses	0	(58)
Fair Value	33,597	48,929
Municipal debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	318,436	189,530
Gross unrealized gains	11,139	1,721
Gross unrealized losses	(24)	(1,035)
Fair Value	329,551	190,216
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,144,217	661,719
Gross unrealized gains	49,583	23,373
Gross unrealized losses	(703)	(211)
Fair Value	1,193,097	684,881
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	130,757	170,153
Gross unrealized gains	2,486	2,603
Gross unrealized losses	(29)	(114)
Fair Value	133,214	172,642
Total bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,624,614	1,069,605
Gross unrealized gains	65,601	28,481
Gross unrealized losses	(756)	(1,418)
Fair Value	1,689,459	1,096,668
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	356	44,174
Gross unrealized gains	0	98
Gross unrealized losses	0	0
Fair Value	$ 356	$ 44,272

Investments - Corporate Debt Se

Investments - Corporate Debt Securities by Industry Group (Details)	Sep. 30, 2020	Dec. 31, 2019
Debt Securities By Industry [Line Items]
Corporate debt securities as component of total (percent)	100.00%	100.00%
Financial
Debt Securities By Industry [Line Items]
Corporate debt securities as component of total (percent)	36.00%	38.00%
Consumer
Debt Securities By Industry [Line Items]
Corporate debt securities as component of total (percent)	24.00%	26.00%
Utilities
Debt Securities By Industry [Line Items]
Corporate debt securities as component of total (percent)	11.00%	9.00%
Communications
Debt Securities By Industry [Line Items]
Corporate debt securities as component of total (percent)	11.00%	10.00%
Technology
Debt Securities By Industry [Line Items]
Corporate debt securities as component of total (percent)	10.00%	7.00%
Industrial
Debt Securities By Industry [Line Items]
Corporate debt securities as component of total (percent)	8.00%	8.00%
Energy
Debt Securities By Industry [Line Items]
Corporate debt securities as component of total (percent)	0.00%	2.00%

Investments - Narrative (Detail

Investments - Narrative (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Unrealized loss position, accumulated loss	$ 756	$ 1,418
Unrealized loss position, 12 months or greater	28	84
OTTI loss in earnings	400
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	$ 5,700	5,500
Unrealized loss position, accumulated loss		58
Unrealized loss position, 12 months or greater		$ 0

Investments - Scheduled Maturit

Investments - Scheduled Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Amortized Cost
Due in one year or less	$ 79,742	$ 138,776
Due after one through five years	479,455	406,986
Due after five through ten years	912,664	380,737
Due after ten years	22,352	17,127
Asset-backed securities	130,757	170,153
Amortized Cost	1,624,970	1,113,779
Fair Value
Due in one year or less	80,330	139,113
Due after one through five years	504,960	417,208
Due after five through ten years	947,919	394,180
Due after ten years	23,392	17,797
Asset-backed securities	133,214	172,642
Fair Value	$ 1,689,815	$ 1,140,940

Investments - Aging of Unrealiz

Investments - Aging of Unrealized Losses (Details) $ in Thousands	Sep. 30, 2020USD ($)security	Dec. 31, 2019USD ($)security
Debt Securities, Available-for-sale [Line Items]
Number of securities, less than 12 months | security	31	49
Fair value, less than 12 months	$ 124,105	$ 154,562
Unrealized losses, less than 12 months	$ (728)	$ (1,334)
Number of securities,12 months or greater | security	2	16
Fair value, 12 months or greater	$ 2,757	$ 27,963
Unrealized losses, 12 months or greater	$ (28)	$ (84)
Number of securities, total | security	33	65
Fair Value	$ 126,862	$ 182,525
Unrealized Losses	$ (756)	$ (1,418)
U.S. Treasury securities and obligations of U.S. government agencies
Debt Securities, Available-for-sale [Line Items]
Number of securities, less than 12 months | security		4
Fair value, less than 12 months		$ 12,001
Unrealized losses, less than 12 months		$ (58)
Number of securities,12 months or greater | security		0
Fair value, 12 months or greater		$ 0
Unrealized losses, 12 months or greater		$ 0
Number of securities, total | security		4
Fair Value		$ 12,001
Unrealized Losses		$ (58)
Municipal debt securities
Debt Securities, Available-for-sale [Line Items]
Number of securities, less than 12 months | security	9	26
Fair value, less than 12 months	$ 15,706	$ 92,844
Unrealized losses, less than 12 months	$ (24)	$ (1,034)
Number of securities,12 months or greater | security	0	1
Fair value, 12 months or greater	$ 0	$ 999
Unrealized losses, 12 months or greater	$ 0	$ (1)
Number of securities, total | security	9	27
Fair Value	$ 15,706	$ 93,843
Unrealized Losses	$ (24)	$ (1,035)
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Number of securities, less than 12 months | security	20	10
Fair value, less than 12 months	$ 101,088	$ 30,481
Unrealized losses, less than 12 months	$ (702)	$ (140)
Number of securities,12 months or greater | security	1	14
Fair value, 12 months or greater	$ 33	$ 23,976
Unrealized losses, 12 months or greater	$ (1)	$ (71)
Number of securities, total | security	21	24
Fair Value	$ 101,121	$ 54,457
Unrealized Losses	$ (703)	$ (211)
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Number of securities, less than 12 months | security	2	9
Fair value, less than 12 months	$ 7,311	$ 19,236
Unrealized losses, less than 12 months	$ (2)	$ (102)
Number of securities,12 months or greater | security	1	1
Fair value, 12 months or greater	$ 2,724	$ 2,988
Unrealized losses, 12 months or greater	$ (27)	$ (12)
Number of securities, total | security	3	10
Fair Value	$ 10,035	$ 22,224
Unrealized Losses	$ (29)	$ (114)

Investments - Net Investment In

Investments - Net Investment Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Investment Income, Net [Abstract]
Investment income	$ 8,624	$ 8,003	$ 24,293	$ 23,240
Investment expenses	(287)	(121)	(782)	(346)
Net investment income	$ 8,337	$ 7,882	$ 23,511	$ 22,894

Investments - Net Realized Inve

Investments - Net Realized Investment Gains (Losses) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Gross realized investment gains	$ 0	$ 81	$ 5,126	$ 297
Gross realized investment losses	(4)	0	(4,491)	(516)
Net realized investment (losses) gains	$ (4)	$ 81	$ 635	$ (219)

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Assets and Liabilities at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	$ 1,689,815	$ 1,140,940
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	33,597	48,929
Municipal debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	329,551	190,216
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	1,193,097	684,881
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	133,214	172,642
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash, cash equivalents and short-term investments	194,555	85,361
Total assets	1,884,014	1,182,029
Warrant liability	3,135	7,641
Total liabilities	3,135	7,641
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	33,597	48,929
Recurring | Municipal debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	329,551	190,216
Recurring | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	1,193,097	684,881
Recurring | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of securities	133,214	172,642
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	194,555	85,361
Total assets	228,152	134,290
Warrant liability	0	0
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	33,597	48,929
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 | 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	1,655,862	1,047,739
Warrant liability	0	0
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	329,551	190,216
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	1,193,097	684,881
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	133,214	172,642
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
Warrant liability	3,135	7,641
Total liabilities	3,135	7,641
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

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Rollforward of Level 3 Liabilities (Details) - Significant Unobservable Inputs (Level 3) - Warrant liability - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Roll-forward of Level 3 liabilities:
Beginning balance	$ 7,641	$ 7,296
Change in fair value of warrant liability included in earnings	(4,286)	6,025
Issuance of common stock on warrant exercise	(220)	(6,957)
Ending balance	$ 3,135	$ 6,364

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	Sep. 30, 2020$ / shares	Sep. 30, 2019$ / shares
Common stock price
Key Inputs and Assumptions, Valuation Techniques
Warrant liability, measurement input	17.80	26.26
Risk free interest rate
Key Inputs and Assumptions, Valuation Techniques
Warrant liability, measurement input	0.0013	0.0176
Expected life
Key Inputs and Assumptions, Valuation Techniques
Warrant liability, expected life	1 year 6 months 21 days	11 months 1 day
Expected volatility
Key Inputs and Assumptions, Valuation Techniques
Warrant liability, measurement input	0.753	0.335
Dividend yield
Key Inputs and Assumptions, Valuation Techniques
Warrant liability, measurement input	0	0

Fair Value of Financial Instr_6

Fair Value of Financial Instruments - Narrative (Details) - Senior debt - USD ($)	Sep. 30, 2020	Jun. 19, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument face amount	$ 400,000,000	$ 400,000,000
Debt	393,000,000		$ 145,800,000
Debt issuance costs	7,000,000	$ 7,400,000	2,000,000
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of long term debt	$ 427,500,000		$ 147,800,000

Debt - Narrative (Details)

Debt - Narrative (Details) - USD ($)	Jun. 19, 2020	Mar. 20, 2020	Mar. 19, 2020	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Debt Instrument [Line Items]
Repayments of term loan						$ 147,750,000	$ 1,125,000
Proceeds from senior secured notes						400,000,000	$ 0
General corporate purposes
Debt Instrument [Line Items]
Proceeds from senior secured notes	$ 244,400,000
2018 Term loan
Debt Instrument [Line Items]
Repayments of term loan	150,000,000
Loss on extinguishment of debt						2,600,000
2018 Revolving credit facility
Debt Instrument [Line Items]
Debt issuance costs			$ 600,000
Revolving credit facility
Debt Instrument [Line Items]
Commitment fees in interest expense				$ 100,000		$ 300,000
Revolving credit facility | 2020 Revolving credit facility
Debt Instrument [Line Items]
Debt instrument covenant, maximum debt-to-total capitalization ratio						35.00%
Credit facility borrowing capacity		$ 100,000,000		100,000,000		$ 100,000,000
Borrowings outstanding				0		0
Commitment fee (in percent)					0.35%
Debt Issuance costs		$ 800,000
Remaining deferred issuance costs, net of accumulated amortization				1,100,000		1,100,000
Revolving credit facility | 2020 Revolving credit facility | Minimum
Debt Instrument [Line Items]
Commitment fee (in percent)		0.175%
Revolving credit facility | 2020 Revolving credit facility | Maximum
Debt Instrument [Line Items]
Commitment fee (in percent)		0.525%
Revolving credit facility | 2020 Revolving credit facility | Base rate
Debt Instrument [Line Items]
Variable rate floor (in percent)		1.00%
Revolving credit facility | 2020 Revolving credit facility | Base rate | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		0.375%
Revolving credit facility | 2020 Revolving credit facility | Base rate | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		1.875%
Revolving credit facility | 2020 Revolving credit facility | Eurodollar
Debt Instrument [Line Items]
Variable rate floor (in percent)		0.00%
Revolving credit facility | 2020 Revolving credit facility | Eurodollar | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		1.375%
Revolving credit facility | 2020 Revolving credit facility | Eurodollar | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		2.875%
Revolving credit facility | 2018 Revolving credit facility
Debt Instrument [Line Items]
Credit facility borrowing capacity			$ 85,000,000
Debt instrument term (years)			3 years
Senior debt
Debt Instrument [Line Items]
Debt instrument face amount	$ 400,000,000			400,000,000		400,000,000
Stated interest rate (in percent)	7.375%
Applicable premium	1.00%
Percent of aggregate balance redeemable with equity offerings	40.00%
Debt issuance costs	$ 7,400,000			7,000,000		7,000,000		$ 2,000,000
Capitalized issuance cost and issue discounts				$ 7,000,000		$ 7,000,000
Debt instrument covenant, maximum debt-to-total capitalization ratio	35.00%
Senior debt | Prior to March 1, 2025
Debt Instrument [Line Items]
Redemption price (in percent)	100.00%
Senior debt | After March 1, 2025
Debt Instrument [Line Items]
Redemption price (in percent)	100.00%
Senior debt | Prior to June 1, 2022
Debt Instrument [Line Items]
Redemption price (in percent)	107.375%

Reinsurance - Effect of Reinsur

Reinsurance - Effect of Reinsurance Agreements on Premiums Written and Earned (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net premiums written
Direct	$ 119,323	$ 100,475	$ 331,254	$ 274,418
Ceded	(17,501)	(11,796)	(47,952)	(31,207)
Net premiums written	101,822	88,679	283,302	243,211
Net premiums earned
Direct	118,552	106,687	351,889	288,165
Ceded	(19,750)	(14,306)	(55,426)	(38,666)
Net premiums earned	$ 98,802	$ 92,381	$ 296,463	$ 249,499

Reinsurance - Narrative (Detail

Reinsurance - Narrative (Details) $ in Thousands	Apr. 01, 2019USD ($)	Mar. 31, 2019	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)quotaShareAgreement	Sep. 30, 2019USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Ceded Credit Risk [Line Items]
Reinsurance coverage, term of underlying mortgage amortization (in years)					10 years
Restricted cash			$ 5,555		$ 5,555		$ 2,662
Number of quota share agreements | quotaShareAgreement					3
Reinsurance recoverable on unpaid claims			$ 17,180	$ 4,309	$ 17,180	$ 4,309	$ 4,939	$ 3,001
ILN transactions
Ceded Credit Risk [Line Items]
Reinsurance coverage amount amortized (as a percent)			10.00%		10.00%
Third-party reinsurers | 2017 ILN transaction
Ceded Credit Risk [Line Items]
Risk premiums paid			$ 6,300	$ 4,400	$ 13,400	$ 10,300
Third-party reinsurers | 2017 ILN transaction | Maximum
Ceded Credit Risk [Line Items]
Anticipated payment related to annual operating expenses					300
Third-party reinsurers | 2018 ILN transaction | Maximum
Ceded Credit Risk [Line Items]
Anticipated payment related to annual operating expenses					$ 250
Third-party reinsurers | QSR transactions
Ceded Credit Risk [Line Items]
Percentage of ceding commission received					20.00%
Reinsurance recoverable on unpaid claims			17,200		$ 17,200
Third-party reinsurers | Risk written policies in 2020
Ceded Credit Risk [Line Items]
Percent of premiums earned under 2018 QSR Transaction					21.00%
Third-party reinsurers | Risk written policies in 2018
Ceded Credit Risk [Line Items]
Percent of premiums earned under 2018 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 RIF recaptured	$ 500,000
Threshold for loss ratio on loans to qualify for profit commission					60.00%
Reinsurance recoverable on unpaid claims			4,800		$ 4,800
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			12,200		$ 12,200
Third-party reinsurers | 2020 QSR transaction
Ceded Credit Risk [Line Items]
Threshold for loss ratio on loans to qualify for profit commission					50.00%
Reinsurance recoverable on unpaid claims			$ 200		$ 200
Third-party reinsurers | Eligible policies, pool one
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%

Reinsurance - ILN Transactions

Reinsurance - ILN Transactions (Details) - USD ($) $ in Thousands	Sep. 30, 2020	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	$ 40,226
Initial First Layer Retained Loss				$ 126,793
Current first layer retained loss	121,602
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	158,489
Initial First Layer Retained Loss			$ 125,312
Current first layer retained loss	123,354
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	231,877
Initial First Layer Retained Loss		123,424
Current first layer retained loss	123,072
2020-1 ILN Transaction
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Initial Reinsurance Coverage		322,076
Current Reinsurance Coverage	322,076
Initial First Layer Retained Loss		$ 169,514
Current first layer retained loss	$ 169,514

Reinsurance - Amounts Related t

Reinsurance - Amounts Related to QSR Transactions (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Ceded Credit Risk [Line Items]
Ceded premiums earned	$ (19,750)	$ (14,306)	$ (55,426)	$ (38,666)
Third-party reinsurers
Ceded Credit Risk [Line Items]
Ceded risk-in-force	5,159,061	4,901,809	5,159,061	4,901,809
Ceded premiums earned	(24,517)	(23,151)	(70,738)	(65,538)
Ceded claims and claim expenses	3,200	766	13,401	2,435
Ceding commission earned	4,798	4,584	13,739	12,961
Profit commission	$ 11,034	$ 13,254	$ 28,718	$ 37,199

Reserves for Insurance Claims_3

Reserves for Insurance Claims and Claim Expenses - Narrative (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2020USD ($)loanclaimpolicy	Sep. 30, 2019USD ($)policyloan	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Liability for Claims and Claims Adjustment Expense [Line Items]
Primary loans in default | loan	13,765	1,230
Total gross liability for unpaid claims and claim adjustment expenses	$ 87,230	$ 20,505	$ 23,752	$ 12,811
Number of claims paid | claim	123
Claims paid, including amounts covered by insurance	$ 5,600
Default percent (in percent)	3.60%	0.35%
Total number of policies in-force | policy	381,899	350,395
Favorable prior year development	$ 5,500	$ 2,710
Reserve for prior year insurance claims and claim expenses	$ 11,400
Fannie Mae
Liability for Claims and Claims Adjustment Expense [Line Items]
Number of loans in pool past due 60 days or more | loan	277
Risk-in-Force of loans in pool past due 60 days or more	$ 23,200
Loan-to-value ratio (less than)	0.80
Claims applied to pool deductible	$ 900
Deductible on policy	$ 9,400
QSR transactions
Liability for Claims and Claims Adjustment Expense [Line Items]
Number of covered claims included in number of claims paid | claim	117
Component of claims paid covered under QSR Transaction	$ 1,200
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_4

Reserves for Insurance Claims and Claim Expenses - Reconciliation of Reserve Balances for Insurance Claims and Claim Expense (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning balance	$ 23,752	$ 12,811
Less reinsurance recoverables	(4,939)	(3,001)
Beginning balance, net of reinsurance recoverables	18,813	9,810
Claims and claim expenses incurred:
Current year	61,198	10,948
Prior years	(5,500)	(2,710)
Total claims and claim expenses incurred	55,698	8,238
Claims and claim expenses paid:
Current year	152	0
Prior years	4,309	2,401
Reinsurance terminations	0	(549)
Total claims and claim expenses paid	4,461	1,852
Reserve at end of period, net of reinsurance recoverables	70,050	16,196
Add reinsurance recoverables	17,180	4,309
Ending balance	$ 87,230	$ 20,505

Earnings per Share (EPS) (Detai

Earnings per Share (EPS) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings per Share, Basic [Abstract]
Net income	$ 38,179	$ 26,848	$ 58,271	$ 49,763	$ 39,100	$ 32,899	$ 123,298	$ 121,762
Basic weighted average shares outstanding (in shares)	84,805			67,849			75,695	67,381
Basic earnings per share (in dollars per share)	$ 0.45			$ 0.73			$ 1.63	$ 1.81
Earnings per Share, Diluted [Abstract]
Net income	$ 38,179	$ 26,848	$ 58,271	$ 49,763	$ 39,100	$ 32,899	$ 123,298	$ 121,762
Gain from change in fair value of warrant liability	0			(1,139)			(4,286)	0
Diluted net income	$ 38,179			$ 48,624			$ 119,012	$ 121,762
Basic weighted average shares outstanding (in shares)	84,805			67,849			75,695	67,381
Dilutive effect of issuable shares (in shares)	794			2,288			1,172	2,139
Dilutive weighted average shares outstanding (in shares)	85,599			70,137			76,867	69,520
Diluted earnings per share (in dollars per share)	$ 0.45			$ 0.69			$ 1.55	$ 1.75
Anti-dilutive shares (in shares)	420			6			91	642

Warrants (Details)

Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	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	$ 3,135		$ 3,135		$ 7,641	$ 5,100
Warrants exercised (in shares)	0	130,000	9,000	390,000
Stock issued upon exercise of warrants (in shares)		82,000	6,000	249,000
Fair value of warrant liability reclassified to additional paid in capital upon exercise		$ 2,200	$ 200	$ 7,000
Change in fair value of warrant liability in current period		$ 900		$ 3,200

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Effective income tax rate on pre-tax income or loss	22.60%	22.20%	21.20%	20.90%
Tax and loss bonds	$ 7.6		$ 7.6

Common Stock (Details)

Common Stock (Details) $ in Millions	Jun. 08, 2020USD ($)shares	Sep. 30, 2020voteshares	Dec. 31, 2019shares
Class of Stock [Line Items]
Common stock, outstanding (in shares)		84,808,516	68,358,074
Number of votes per common share | vote		1
Over-allotment option | Common stock
Class of Stock [Line Items]
Over-allotment option to purchase shares (in percent)	15.00%
Public stock offering | Common stock
Class of Stock [Line Items]
Number of shares sold (in shares)	13,800,000
Net proceeds of sale of stock | $	$ 219.7
Public stock offering and over allotment option | Common stock
Class of Stock [Line Items]
Number of shares sold (in shares)	15,900,000

Regulatory Information - Statut

Regulatory Information - Statutory Net Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
NMIC and Re One combined
Statutory Accounting Practices [Line Items]
Statutory net (loss) gain	$ (5,600)	$ 8,055	$ (22,614)	$ 13,594

Regulatory Information - Schedu

Regulatory Information - Schedule of Statutory Surplus, Contingency Reserve and RTC Ratio (Details) - NMIC and Re One combined $ in Thousands	Sep. 30, 2020USD ($)	Dec. 31, 2019USD ($)
Statutory Accounting Practices [Line Items]
Statutory surplus	$ 883,580	$ 449,602
Contingency reserve	707,769	531,825
Statutory capital	$ 1,591,349	$ 981,427
RTC ratio	12.5	15.8

Regulatory Information - Narrat

Regulatory Information - Narrative (Details) - USD ($)	Jun. 19, 2020	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Mar. 20, 2020
Statutory Accounting Practices [Line Items]
Proceeds from senior secured notes		$ 400,000,000	$ 0
Revolving credit facility | 2020 Revolving credit facility
Statutory Accounting Practices [Line Items]
Credit facility borrowing capacity		100,000,000			$ 100,000,000
NMIC
Statutory Accounting Practices [Line Items]
Proceeds from senior secured notes	$ 445,000,000
Senior debt
Statutory Accounting Practices [Line Items]
Debt instrument face amount	$ 400,000,000	$ 400,000,000
NMIC and Re One combined | Forecast
Statutory Accounting Practices [Line Items]
Aggregate dividend capacity				$ 16,100,000

Subsequent Event (Details)

Subsequent Event (Details) - USD ($)	Oct. 29, 2020	Nov. 05, 2020	Oct. 30, 2020	Sep. 30, 2020	Mar. 20, 2020
Revolving credit facility | 2020 Revolving credit facility
Subsequent Event [Line Items]
Credit facility borrowing capacity				$ 100,000,000	$ 100,000,000
Subsequent Event
Subsequent Event [Line Items]
Amount retained	$ 121,200,000
Subsequent Event | Revolving credit facility | 2020 Revolving credit facility
Subsequent Event [Line Items]
Credit facility borrowing capacity	100,000,000		$ 110,000,000
Amount outstanding		$ 0
Subsequent Event | Maximum
Subsequent Event [Line Items]
Annual risk premium payments, capped amount	250,000
Subsequent Event | Maximum | Oaktown Re IV Ltd.
Subsequent Event [Line Items]
Amount reinsured	242,400,000
Subsequent Event | Mortgage insurance-linked notes | Oaktown Re IV Ltd.
Subsequent Event [Line Items]
Debt instrument face amount	$ 242,400,000