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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2017	May 02, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	NMI HOLDINGS, INC.
Entity Central Index Key	0001547903
Document Type	10-Q
Document Period End Date	Mar. 31, 2017
Amendment Flag	false
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		59,785,313

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Assets
Fixed maturities, available-for-sale, at fair value (amortized cost of $658,463 and $630,688 as of March 31, 2017 and December 31, 2016, respectively)	$ 658,640	$ 628,969
Cash and cash equivalents	12,543	47,746
Premiums receivable	15,566	13,728
Accrued investment income	3,900	3,421
Prepaid expenses	2,935	1,991
Deferred policy acquisition costs, net	32,165	30,109
Software and equipment, net	21,168	20,402
Intangible assets and goodwill	3,634	3,634
Prepaid reinsurance premiums	38,348	37,921
Deferred tax asset, net	50,529	51,434
Other assets	734	542
Total assets	840,162	839,897
Liabilities
Term loan	144,010	144,353
Unearned premiums	154,711	152,906
Accounts payable and accrued expenses	14,175	25,297
Reserve for insurance claims and claim expenses	3,761	3,001
Reinsurance funds withheld	31,243	30,633
Deferred ceding commission	4,790	4,831
Warrant liability, at fair value	3,563	3,367
Total liabilities	356,253	364,388
Commitments and contingencies
Shareholders' Equity
Additional paid-in capital	578,081	576,927
Accumulated other comprehensive loss, net of tax	(4,054)	(5,287)
Accumulated deficit	(90,716)	(96,722)
Total shareholders' equity	483,909	475,509
Total liabilities and shareholders' equity	840,162	839,897
Common Stock - Class A
Shareholders' Equity
Common stock - class A shares, $0.01 par value; 59,783,358 and 59,145,161 shares issued and outstanding as of March 31, 2017 and December 31, 2016, respectively (250,000,000 shares authorized)	$ 598	$ 591

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fixed maturities, amortized cost	$ 658,463	$ 630,688
Common Stock - Class A
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares issued (in shares)	59,783,358	59,145,161
Common stock, shares outstanding (in shares)	59,783,358	59,145,161
Common stock, shares authorized (in shares)	250,000,000	250,000,000

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenues
Net premiums earned	$ 33,225	$ 19,807
Net investment income	3,807	3,231
Net realized investment losses	(58)	(885)
Other revenues	80	32
Total revenues	37,054	22,185
Expenses
Insurance claims and claims expenses	635	458
Underwriting and operating expenses	25,989	22,672
Total expenses	26,624	23,130
Other (expense) income
(Loss) gain from change in fair value of warrant liability	(196)	670
Interest expense	(3,494)	(3,632)
Total other expense	(3,690)	(2,962)
Income (loss) before income taxes	6,740	(3,907)
Income tax expense	1,248	0
Net income (loss)	$ 5,492	$ (3,907)
Earnings (loss) per share
Basic earnings (loss) per share (in dollars per share)	$ 0.09	$ (0.07)
Diluted earnings (loss) per share (in dollars per share)	$ 0.09	$ (0.07)
Weighted average common shares outstanding
Basic weighted average shares outstanding (in shares)	59,183,973	58,936,694
Dilutive weighted average shares outstanding (in shares)	62,338,856	58,936,694
Other comprehensive income, net of tax:
Net unrealized gains in accumulated other comprehensive income, net of tax expense of $664 and $0 for the quarters ended March 31, 2017 and March 31, 2016, respectively	$ 1,175	$ 9,101
Reclassification adjustment for losses included in net loss (gain), net of tax expense of $0 for the quarters ended March 31, 2017 and 2016	58	885
Other comprehensive income, net of tax	1,233	9,986
Comprehensive income	$ 6,725	$ 6,079

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (UNAUDITED) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Statement [Abstract]
Net unrealized investment gains in AOCI, tax amount	$ 664	$ 0
Reclassification adjustment for losses included in net loss (gain), tax amount	$ 0	$ 0

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock Class A	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2015	$ 402,731	$ 588	$ 570,340	$ (7,474)	$ (160,723)
Beginning balance (in shares) at Dec. 31, 2015		58,808
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes	(224)	$ 3	(227)
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes (in shares)		337
Share-based compensation expense	6,814		6,814
Change in unrealized investment gains/losses, net of tax	2,187			2,187
Net income	64,001				64,001
Ending balance at Dec. 31, 2016	475,509	$ 591	576,927	(5,287)	(96,722)
Ending balance (in shares) at Dec. 31, 2016		59,145
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle	514				514
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes	(1,110)	$ 7	(1,117)
Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes (in shares)		638
Share-based compensation expense	2,271		2,271
Change in unrealized investment gains/losses, net of tax	1,233			1,233
Net income	5,492				5,492
Ending balance at Mar. 31, 2017	$ 483,909	$ 598	$ 578,081	$ (4,054)	$ (90,716)
Ending balance (in shares) at Mar. 31, 2017		59,783

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (UNAUDITED) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Statement of Stockholders' Equity [Abstract]
Change in unrealized investment gains/losses, tax	$ 664	$ 0	$ 1,178

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities
Net income (loss)	$ 5,492	$ (3,907)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Net realized investment losses	58	885
Loss (gain) from change in fair value of warrant liability	196	(670)
Depreciation and amortization	1,502	990
Net amortization of premium on investment securities	357	326
Amortization of debt discount and debt issuance costs	403	418
Share-based compensation expense	1,911	1,410
Changes in operating assets and liabilities:
Accrued investment income	(479)	(271)
Premiums receivable	(1,838)	(1,435)
Prepaid expenses	(944)	(1,304)
Deferred policy acquisition costs, net	(2,056)	(3,418)
Other assets	(192)	16
Deferred tax asset	1,146	0
Unearned premiums	1,805	18,322
Reserve for insurance claims and claims expenses	760	458
Reinsurance balances, net	141	0
Accounts payable and accrued expenses	(10,351)	(11,085)
Net cash (used in) provided by operating activities	(2,089)	735
Cash flows from investing activities
Purchase of short-term investments	(38,663)	(40,234)
Purchase of fixed-maturity investments, available-for-sale	(60,212)	(31,085)
Proceeds from maturity of short-term investments	46,845	24,347
Proceeds from redemptions, maturities and sale of fixed-maturity investments, available-for-sale	23,841	65,075
Software and equipment	(3,069)	(2,319)
Net cash (used in) provided by investing activities	(31,258)	15,784
Cash flows from financing activities
Proceeds from issuance of common stock related to employee equity plans	2,392	449
Taxes paid related to net share settlement of equity awards	(3,503)	(608)
Repayments of term loan	(375)	(375)
Payments of debt modification costs	(370)	0
Net cash used in financing activities	(1,856)	(534)
Net (decrease) increase in cash and cash equivalents	(35,203)	15,985
Cash and cash equivalents, beginning of period	47,746	57,317
Cash and cash equivalents, end of period	12,543	73,302
Noncash financing activities
Interest paid	3,314	3,225
Taxes paid	$ 170	$ 0

Organization and Basis of Presentation

3 Months Ended

Mar. 31, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Organization and Basis of Presentation

NMI Holdings, Inc. (NMIH) is a Delaware corporation, incorporated in May 2011, to provide private mortgage guaranty insurance (which we refer to as mortgage insurance or MI) through its wholly owned insurance subsidiaries, National Mortgage Insurance Corporation (NMIC) and National Mortgage Reinsurance Inc One (Re One). In April 2012, we completed a private placement of our securities, through which we offered and sold an aggregate of 55,000,000 of our Class A common stock resulting in net proceeds of approximately $510 million (the Private Placement), and we completed the acquisition of our insurance subsidiaries for $8.5 million in cash, common stock and warrants, plus the assumption of $1.3 million in liabilities. In November 2013, we completed an initial public offering of 2.4 million shares of our common stock, and our common stock began trading on the NASDAQ exchange on November 8, 2013, under the 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 on a limited basis 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, 2016, included in our 2016 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. 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, 2017.

Deferred Policy Acquisition Costs

Costs directly associated with the successful acquisition of mortgage insurance policies, consisting of certain selling expenses and other policy issuance and underwriting expenses, are initially deferred and reported as deferred policy acquisition costs (DAC). DAC is reviewed periodically to determine that it does not exceed recoverable amounts and is adjusted as appropriate for policy cancellations to be consistent with our revenue recognition policy. We estimate the rate of amortization to reflect actual experience and any changes to persistency or loss development. For each book year of business, these costs are amortized to expense in proportion to estimated gross profits over the estimated life of the policies. Total amortization of DAC for the three months ended March 31, 2017 and 2016, net of a portion of ceding commission related to the 2016 QSR Transaction (see Note 5, "Reinsurance"), was $1.0 million and $0.9 million, respectively.

Premium Deficiency Reserves

We consider whether a premium deficiency exists at each fiscal quarter using best estimate assumptions as of the testing date. Per ASC 944, a premium deficiency reserve shall be recognized if the sum of expected claim costs and claim adjustment expenses, expected dividends to policyholders, unamortized acquisition costs, and maintenance costs exceeds related unearned premiums and anticipated investment income. We have determined that no premium deficiency reserves were necessary for the three months ended March 31, 2017 or 2016.

Reinsurance

We account for premiums, losses and loss expenses that are ceded to reinsurers on bases consistent with those we use to account for the original policies we issue and pursuant to the terms of our reinsurance contracts. We account for premiums ceded to reinsurers as reductions to premium revenue. We earn profit commissions, which represent a percentage of the profits recognized by the reinsurers that are returned to us, based on the level of losses ceded. We recognize any profit commissions we earn as increases in net premium revenue.

We receive ceding commissions, calculated as a percentage of ceded written premiums, which are intended to cover our costs to acquire and service the direct policies. We earn the ceding commissions 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 as reductions to underwriting and operating expenses.

We cede a portion of loss reserves, paid losses and loss expenses, which are accounted for as reductions to loss expense and as reinsurance recoverables. We remain directly liable for all loss payments in the event we are unable to collect from any reinsurer.

Premiums Receivable

Premiums receivable consist of premiums due on our mortgage insurance policies. If a mortgage insurance premium is unpaid for more than 120 days, the receivable is written off against earned premium and the related insurance policy is canceled.

Recent Accounting Pronouncements

In May 2014, the Financial accounting Standards Board (the FASB) issued Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers (Topic 606). This update is intended to provide a consistent approach in recognizing revenue. In accordance with the new standard, recognition of revenue occurs when a customer obtains control of promised goods or services in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In addition, the new standard requires that reporting companies disclose the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. In August 2015, ASU 2015-14 deferred the provisions of ASU 2014-09 to be effective for interim and annual periods beginning after December 15, 2017. In addition, this guidance amends the existing requirements for the recognition of a gain or loss on the transfer of non-financial assets that are not in a contract with a customer (ASU 2017-05). The Company is currently evaluating the impact the adoption of this ASU will have, if any, on the consolidated financial statements; however, this update is not expected to impact the recognition of revenue related to insurance premiums or investments, which represent the majority of our total revenues.

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). This update requires that businesses recognize rights and obligations associated with certain leases as assets and liabilities on the balance sheet.The standard also requires additional disclosures regarding the amount, timing, and uncertainty of cash flows arising from leases. For public business entities, this update is effective for annual periods beginning after December 15, 2018 and interim periods therein. Early adoption is permitted in any period. We expect to adopt this guidance on January 1, 2019. We anticipate this standard will have a material impact on our financial position, primarily due to our office space operating lease, as we will be required to recognize lease assets and lease liabilities on our consolidated balance sheet. We will continue to assess the potential impacts of this standard, including the impact the adoption of this guidance will have on our results of operations or cash flows.

In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326). This update requires companies to measure all expected credit losses for financial assets held at the reporting date. The accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration also is amended in the standard. The standard will take effect for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. The Company is currently in the early stages of evaluating the impact the adoption of this ASU will have, if any, on the consolidated financial statements.

In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230). This update is intended to reduce diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The standard will take effect for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017. The Company is currently in the early stages of evaluating the impact the adoption of this ASU will have, if any, on the consolidated financial statements.

In August 2016, the FASB issued ASU 2016-16, Income Taxes- Intra-Entity Transfers of Assets Other Than Inventory (Topic 740). This update is intended to improve the accounting for the income tax consequences of intra-entity transfers of assets other than inventory. The standard will take effect for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017. Early adoption is permitted at the beginning of any annual reporting period. The Company is currently in the early stages of evaluating the impact the adoption of this ASU will have, if any, on the consolidated financial statements.

In January 2017, the FASB issued ASU 2017-04, Intangibles - Goodwill and Other (Topic 350). This update is intended to simplify the test for goodwill impairment. The standard will take effect for public business entities for fiscal years, and interim periods within those fiscal years, after December 15, 2020. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company is currently in the early stages of evaluating the impact the adoption of this ASU will have, if any, on the consolidated financial statements.

In March 2017, the FASB issued ASU 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20). This update shortens the amortization period for the premium on certain purchased callable debt securities to the earliest call date. The standard will take effect for public business entities for fiscal years beginning after December 15, 2017. Early adoption is permitted, and if an entity early adopts the guidance in an interim period, any adjustments are reflected as of the beginning of the fiscal year that includes that interim period. The Company is currently in the early stages of evaluating the impact the adoption of this ASU will have, if any, on the consolidated financial statements.

Immaterial Correction of Prior Period Amounts

During the first quarter of 2017, after filing its 2016 10-K, including the audited financial statements included therein, the Company discovered that $1.8 million of deferred taxes on vested options associated with employees who had terminated employment in previous years had not been reversed. Because the Company’s deferred tax asset (DTA) was subject to a valuation allowance prior to December 2016, no expense would have been recognized by the Company in periods prior to December 2016. However, at December 31, 2016, when the Company released the valuation allowance against its DTA, the DTA was overstated by $1.8 million. The release of the valuation allowance resulted in a $1.8 million overstatement of the Company’s 2016 income tax benefit and net income.

In order to provide consistency in the consolidated statements and as permitted by Staff Accounting Bulletin (SAB) 108, revisions for these immaterial amounts to previously reported annual amounts are reflected in the Consolidated Balance Sheet financial information herein and will be reflected in the Consolidated Statement of Operations in future filings containing such financial information as permitted by SAB 108. A comparison of the effected amounts as reported and as adjusted are reported below.



As of and for the full year ended December 31, 2016	As previously reported			As adjusted
	(In thousands)
Income Statement
Net income	$	65,841		$	64,001
Income tax (benefit)	(54,389		)	(52,550		)
Basic EPS	1.11			1.08
Diluted EPS	1.08			1.05

Balance Sheet
Deferred tax asset, net	$	53,274		$	51,434
Total assets	841,737			839,897
Accumulated deficit	(94,882		)	(96,722		)
Total shareholder's equity	477,349			475,509

Change in Accounting Principle

In March 2016, the FASB issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting (Topic 718), which intends to simplify various aspects of the accounting for and reporting of share-based payments. The new accounting is required to be adopted using a modified retrospective approach, with a cumulative-effect adjustment to opening retained earnings for any outstanding liability awards that qualify for equity classification under the new guidance.

As the guidance is effective for annual and interim reporting periods beginning after December 15, 2016, the Company adopted the new guidance in the first quarter of 2017. This requires us to reflect any adjustments as of January 1, 2017, the beginning of the annual period that includes the interim period of adoption. The primary impact of adoption was the recognition of excess tax benefits in our provision for income taxes in our consolidated statement of earnings. Additionally, our consolidated statement of cash flows now present excess tax benefits as an operating activity on a prospective basis. Finally, we have elected to account for forfeitures as they occur, rather than estimate expected forfeitures. The net cumulative effect of this change was recognized as a $0.5 million reduction to the retained deficit as of January 1, 2017.

Subsequent Event

On May 2, 2017, we entered into an excess of loss reinsurance agreement with Oaktown Re Ltd., a Bermuda-domiciled special purpose insurer. In connection with the transaction, NMIC will receive $211.3 million of fully collateralized excess of loss reinsurance protection, covering an existing portfolio of mortgage insurance policies written from 2013 through 2016. In connection with the note offering, as is customary in such capital markets transactions, NMIH indemnified the underwriter with respect to information provided in the offering materials about NMIC and the reinsured loans.

Investments

3 Months Ended

Mar. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Investments

We have designated our investment portfolio as available-for-sale and report it at fair value. The related unrealized gains and losses are, after considering the related tax expense or benefit, recognized as a component of accumulated other comprehensive income and loss in shareholders' equity. Net realized investment gains and losses are reported in income based upon specific identification of securities sold.

Fair Values and Gross Unrealized Gains and Losses on Investments



	Amortized Cost		Gross Unrealized					Fair Value
	Amortized Cost		Gains		Losses			Fair Value
As of March 31, 2017	(In Thousands)
U.S. Treasury securities and obligations of U.S. government agencies	$	66,555	$	3	$	(850	)	$	65,708
Municipal debt securities	70,543		316		(463		)	70,396
Corporate debt securities	360,955		2,466		(1,781		)	361,640
Asset-backed securities	107,008		696		(313		)	107,391
Total bonds	605,061		3,481		(3,407		)	605,135
Short-term investments	53,402		103		—			53,505
Total investments	$	658,463	$	3,584	$	(3,407	)	$	658,640



	Amortized Cost		Gross Unrealized					Fair Value
	Amortized Cost		Gains		Losses			Fair Value
As of December 31, 2016	(In Thousands)
U.S. Treasury securities and obligations of U.S. government agencies	$	64,135	$	6	$	(962	)	$	63,179
Municipal debt securities	40,801		131		(663		)	40,269
Corporate debt securities	349,712		1,722		(2,356		)	349,078
Asset-backed securities	114,456		765		(560		)	114,661
Total bonds	569,104		2,624		(4,541		)	567,187
Short-term investments	61,584		198		—			61,782
Total investments	$	630,688	$	2,822	$	(4,541	)	$	628,969

As of March 31, 2017 and December 31, 2016, there were approximately $6.9 million of cash and investments in the form of U.S. Treasury securities on deposit with various state insurance departments to satisfy regulatory requirements.

Scheduled Maturities

The amortized cost and fair values of available for sale securities as of March 31, 2017 and December 31, 2016, 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 separate categories.



As of March 31, 2017	Amortized Cost		Fair Value
	(In Thousands)
Due in one year or less	$	120,819	$	120,890
Due after one through five years	147,875		148,565
Due after five through ten years	266,793		266,076
Due after ten years	15,968		15,718
Asset-backed securities	107,008		107,391
Total investments	$	658,463	$	658,640



As of December 31, 2016	Amortized Cost		Fair Value
	(In Thousands)
Due in one year or less	$	94,382	$	94,584
Due after one through five years	173,296		173,251
Due after five through ten years	242,005		240,060
Due after ten years	6,549		6,413
Asset-backed securities	114,456		114,661
Total investments	$	630,688	$	628,969

Aging of Unrealized Losses

As of March 31, 2017, the investment portfolio had gross unrealized losses of $3.4 million, $0.4 million of which has been in an unrealized loss position for a period of 12 months or greater. We did not consider these securities to be other-than-temporarily impaired as of March 31, 2017. We based our conclusion that these investments were not other-than-temporarily impaired as of March 31, 2017 on the following facts: (i) the unrealized losses were primarily caused by interest rate movements since the purchase date; (ii) we do not intend to sell these investments; and (iii) we do not believe that it is more likely than not that we will be required to sell these investments before recovery of our amortized cost basis, which may not occur until maturity. For those securities in an unrealized loss position, the length of time the securities were in such a position is as follows:



	Less Than 12 Months						12 Months or Greater						Total
	# of Securities	Fair Value		Unrealized Losses			# of Securities	Fair Value		Unrealized Losses			# of Securities	Fair Value		Unrealized Losses
As of March 31, 2017		(Dollars in Thousands)
U.S. Treasury securities and obligations of U.S. government agencies	37	$	61,703	$	(850	)	—	$	—	$	—		37	$	61,703	$	(850	)
Municipal debt securities	14	27,663		(431		)	1	1,718		(32		)	15	29,381		(463		)
Corporate debt securities	60	100,085		(1,465		)	6	11,022		(316		)	66	111,107		(1,781		)
Asset-backed securities	23	29,086		(241		)	10	8,547		(72		)	33	37,633		(313		)
Total investments	134	$	218,537	$	(2,987	)	17	$	21,287	$	(420	)	151	$	239,824	$	(3,407	)



	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, 2016		(Dollars in Thousands)
U.S. Treasury securities and obligations of U.S. government agencies	33	$	51,093	$	(962	)	—	$	—	$	—		33	$	51,093	$	(962	)
Municipal debt securities	14	28,659		(617		)	1	1,704		(46		)	15	30,363		(663		)
Corporate debt securities	77	135,115		(1,955		)	8	13,873		(401		)	85	148,988		(2,356		)
Asset-backed securities	30	38,702		(510		)	6	2,472		(50		)	36	41,174		(560		)
Total investments	154	$	253,569	$	(4,044	)	15	$	18,049	$	(497	)	169	$	271,618	$	(4,541	)

Net Investment Income



	For the three months ended March 31,
	2017			2016
	(In Thousands)
Investment income	$	3,993		$	3,408
Investment expenses	(186		)	(178		)
Net investment income	$	3,807		$	3,231

Net Realized Investment Gains (Losses)



	For the three months ended March 31,
	2017			2016
	(In Thousands)
Gross realized investment gains	$	279		$	556
Gross realized investment losses	(337		)	(1,441		)
Net realized investment losses	$	(58	)	$	(885	)

Investment Securities - Other-than-Temporary Impairment (OTTI)

For the quarter ended March 31, 2017, we recognized an OTTI loss in earnings of $144 thousand based on a negative outlook with an unfavorable forecasted recovery.

There were no credit losses recognized in earnings for which a portion of an OTTI loss was recognized in accumulated other comprehensive income (loss).

- Definition

The entire disclosure for investments in certain debt and equity securities.

+ References + Details

Fair Value of Financial Instruments

3 Months Ended

Mar. 31, 2017

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

The following describes the valuation techniques used by us to determine the fair value of financial instruments held at March 31, 2017 and December 31, 2016:

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 - Unadjusted quoted prices for identical assets or liabilities in active markets that are accessible at the measurement date for identical assets or liabilities. Financial assets utilizing Level 1 inputs are U.S. Treasury securities;

Level 2 - Prices or valuations based on observable inputs other than quoted prices in active markets for identical assets and liabilities. Financial assets utilizing Level 2 inputs include certain obligations of U.S. government agencies, municipal and corporate debt securities and asset-backed securities; and

Level 3 - Unobservable inputs that are significant to the fair value of the assets or liabilities. Level 3 assets and liabilities include financial instruments whose value is determined using pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant management judgment or estimation. We value our warrant liability utilizing Level 3 inputs.

The level of market activity used to determine the fair value hierarchy is based on the availability of observable inputs market participants would use to price an asset or a liability, including market value price observations.

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. There were no transfers between Level 1 and Level 2 of the fair value hierarchy during the quarter ended March 31, 2017.

Liabilities classified as Level 3

We calculate the fair value of outstanding warrants using a Black-Scholes option-pricing model in combination with a binomial model. Variables in the model include the risk-free rate of return, dividend yield, expected life and expected volatility of our stock price.

ASC 825, Disclosures about Fair Value of Financial Instruments, requires all entities to disclose the fair value of their financial instruments, both assets and liabilities recognized and not recognized in the balance sheet, for which it is practicable to estimate fair value.

The following is a list of those assets and liabilities that are measured at fair value by hierarchy level:



	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Fair Value
As of March 31, 2017	(In Thousands)
U.S. Treasury securities and obligations of U.S. government agencies	$	55,746	$	9,962	$	—	$	65,708
Municipal debt securities	—		70,396		—		70,396
Corporate debt securities	—		361,640		—		361,640
Asset-backed securities	—		107,391		—		107,391
Cash, cash equivalents and short-term investments	66,048		—		—		66,048
Total assets	$	121,794	$	549,389	$	—	$	671,183
Warrant liability	—		—		3,563		3,563
Total liabilities	$	—	$	—	$	3,563	$	3,563



	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Fair Value
As of December 31, 2016	(In Thousands)
U.S. Treasury securities and obligations of U.S. government agencies	$	50,719	$	12,460	$	—	$	63,179
Municipal debt securities	—		40,269		—		40,269
Corporate debt securities	—		349,078		—		349,078
Asset-backed securities	—		114,661		—		114,661
Cash, cash equivalents and short-term investments	109,528		—		—		109,528
Total assets	$	160,247	$	516,468	$	—	$	676,715
Warrant liability	—		—		3,367		3,367
Total liabilities	$	—	$	—	$	3,367	$	3,367

The following is a roll-forward of Level 3 liabilities measured at fair value:



	For the three months ended March 31,
Warrant Liability	2017		2016
	(In Thousands)
Balance, January 1	$	3,367	$	1,467
Change in fair value of warrant liability included in earnings	196		(670		)
Balance, March 31	$	3,563	$	797

We revalue the warrant liability quarterly using 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. As of March 31, 2017, the assumptions used in the option-pricing model were as follows: a common stock price as of March 31, 2017 of $11.40, risk free interest rate of 1.70%, expected life of 3.92 years, expected volatility of 30.5% and a dividend yield of 0%. The change in fair value is primarily attributable to an increase in the price of our common stock from December 31, 2016 to March 31, 2017.

- Definition

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

+ References + Details

Term Loan

3 Months Ended

Mar. 31, 2017

Debt Disclosure [Abstract]

Term Loan

On November 10, 2015, the Company entered into a credit agreement (the Credit Agreement) to obtain a three-year senior secured term loan B (the Term Loan) for $150 million. On February 10, 2017, we entered into an amendment to the Credit Agreement, to extend the maturity date by one year and reduce the interest rate. We performed an analysis and concluded the amendment to the Credit Agreement should be treated as a modification. As of March 31, 2017, the Term Loan bears interest at the Eurodollar Rate, as defined in the Credit Agreement, (1% floor) plus an annual margin rate of 6.75% (an all-in rate of 8.0% as of March 31, 2017), payable quarterly. Quarterly principal payments of $375 thousand are also required. The outstanding balance as of March 31, 2017 was $147.8 million.

Debt issuance costs totaling $4.8 million and a 1% debt discount are being amortized to interest expense, using the effective interest method, over the contractual life of the Term Loan, including $370 thousand related to the modification. Effective interest rate for the Term Loan includes interest, amortization of issuance cost and the discount. For the three months ended March 31, 2017, the Company recorded $3.5 million of interest expense, including amortization of the issuance cost and discount.

NMIH is subject to certain quarterly covenants under the Credit Agreement. These covenants include, but are not limited to the following: a maximum debt-to-total capitalization ratio (as defined) of 35%, maximum risk-to-capital (RTC) ratio of 22.0:1.0, liquidity (as defined) of $33.4 million as of March 31, 2017, compliance with the PMIERs financial requirements (subject to any GSE-approved waivers), and equity requirements. This description is not intended to be complete in all respects and is qualified in its entirety by the terms of the Credit Agreement, including its covenants and events of default. We were in compliance with all covenants as of March 31, 2017.

Future principal payments for the Company's Term Loan as of March 31, 2017 are as follows:



As of March 31, 2017	Principal
	(In thousands)
2017	$	1,125
2018	1,500
2019	145,125
Total	$	147,750

Reinsurance

3 Months Ended

Mar. 31, 2017

Reinsurance Disclosures [Abstract]

Reinsurance

In September 2016, in order to continue to grow our business and manage insurance risk and our minimum required assets under PMIERs financial requirements, the Company entered into a quota-share reinsurance transaction with a panel of third-party reinsurers, subject to certain conditions (2016 QSR Transaction). Each of the third-party reinsurers has an insurer financial strength rating of A- or better by Standard and Poor’s Rating Services (S&P), A.M. Best or both. The GSEs and the Wisconsin Office of the Commissioner of Insurance (Wisconsin OCI) approved the 2016 QSR Transaction (subject to certain conditions), giving full capital credit under PMIERs and statutory accounting principles, respectively, for the risk ceded under the agreement. The credit that we receive under PMIERs is subject to periodic review by the GSEs.

Under the 2016 QSR Transaction, effective September 1, 2016, NMIC ceded premiums related to:

•25% of existing risk written on eligible policies as of August 31, 2016;


•	100% of our existing risk under our pool agreement with Fannie Mae; and


•	25% of risk on eligible policies written from September 1, 2016 through December 31, 2017.

The effect of reinsurance on net premiums written and earned is as follows:



	For the three months ended
	March 31, 2017			March 31, 2016
	(In Thousands)
Net premiums written
Direct	$	39,245		$	38,129
Ceded	(4,641		)	—
Net premiums written	$	34,604		$	38,129

Net premiums earned
Direct	$	37,438		$	19,807
Ceded	(4,213		)	—
Net premiums earned	$	33,225		$	19,807

The following tables show the amounts ceded related to the 2016 QSR Transaction:



	For the three months ended
	March 31, 2017			March 31, 2016
	(In Thousands)
Ceded risk-in-force	$	2,167,745		$	—
Ceded premiums written	(4,641		)	—
Ceded premiums earned	(4,213		)	—
Ceding commission written	2,058			—
Ceding commission earned	2,065			—

NMIC receives a 20% ceding commission for premiums ceded pursuant to this transaction. NMIC will also receive a profit commission, provided that the loss ratio on the loans covered under the agreement generally remains below 60%, as measured annually. Losses on the ceded risk reduce NMIC's profit commission 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. Ceded premiums written are recorded on the balance sheet as prepaid reinsurance premiums and amortized to ceded premiums earned in a manner consistent with the recognition of income on direct premiums.

The reinsurance recoverable on loss reserves related to our 2016 QSR Transaction was $564 thousand as of March 31, 2017. The reinsurance recoverable balance is further supported by trust accounts established and maintained by each reinsurer in accordance with the PMIERs funding requirements that address ceded risk.

The agreement 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. However, NMIC has the option, based on certain conditions and subject to a termination fee, to terminate the agreement as of December 31, 2020, or at the end of any calendar quarter thereafter, which would result in NMIC reassuming the related risk.

- Definition

The entire disclosure pertaining to the existence, magnitude and information about insurance that has been ceded to or assumed from another insurance company, including the methodologies and assumptions used in determining recorded amounts.

+ References + Details

Reserves for Insurance Claims and Claim Expenses

3 Months Ended

Mar. 31, 2017

Insurance [Abstract]

Reserves for Insurance Claims and Claim Expenses

Reserves for Insurance Claims and Claims Expenses

We establish claim reserves to recognize the estimated liability for insurance claims and claim expenses related to defaults on insured mortgage loans. Our method, consistent with industry practice, is to establish claim reserves only for loans that have been reported to us as having been in default for at least 60 days. Our claim reserves also include amounts for estimated claims incurred on loans that have been in default for at least 60 days that have not yet been reported to us by the servicers, often referred to as IBNR. As of March 31, 2017, we have established reserves for insurance claims and claims expenses of $3.8 million for 207 primary loans in default. We paid 4 claims totaling $142 thousand during the quarter ended March 31, 2017.

In 2013, we entered into a pool insurance transaction with Fannie Mae. We only establish claim or IBNR reserves for pool risk if we expect claims to exceed the deductible under the pool agreement, which represents the amount of claims absorbed by Fannie Mae before we are obligated to pay any claims. At March 31, 2017, 47 loans in the pool were past due by 60 days or more. These 47 loans represent approximately $3.1 million in risk-in-force (RIF). Due to the size of the remaining deductible of $10.1 million, the low level of notices of default (NODs) reported through March 31, 2017 and the expected severity (all loans in the pool have loan-to-value ratios (LTVs) under 80%), we have not established any pool reserves for claims or IBNR for the three months ended March 31, 2017 and 2016. In connection with settlement of pool claims, we applied $256 thousand to the pool deductible through March 31, 2017. We have not paid any pool claims to date.

The following table provides a reconciliation of the beginning and ending reserve balances for primary insurance claims and claims expenses:



	For the three months ended March 31,
	2017			2016
	(In Thousands)
Beginning balance	$	3,001		$	679
Less reinsurance recoverables ⁽¹⁾	(297		)	—
Beginning balance, net of reinsurance recoverables	2,704			679

Add claims incurred:
Claims and claim expenses incurred:
Current year ⁽²⁾	955			553
Prior years⁽³⁾	(320		)	(95		)
Total claims and claims expenses incurred	635			458

Less claims paid:
Claims and claim expenses paid:
Current year ⁽²⁾	—			—
Prior years ⁽³⁾	142			—
Total claims and claim expenses paid	142			—

Reserve at end of period, net of reinsurance recoverables	3,197			1,137
Add reinsurance recoverables ⁽¹⁾	564			—
Balance, March 31	$	3,761		$	1,137

⁽¹⁾ Related to ceded losses recoverable on the 2016 QSR Transaction, included in "Other Assets" on the Condensed Consolidated Balance Sheets. See Note 5, "Reinsurance" for additional information.

⁽²⁾ Related to defaults occurring in the current year.

⁽³⁾ Related to defaults occurring in prior years.

The “claims incurred” section of the table above shows claims and claim expenses incurred on default notices received in the current year and in prior years. The amount of claims incurred relating to default notices received in the current year represents the estimated amount to be ultimately paid on such default notices. The decreases during the periods presented in reserves held for prior year defaults are generally the result of ongoing analysis of recent loss development trends. We may increase or decrease our original estimates as we learn additional information about individual defaults and claims.

There was a $320 thousand favorable prior year development during the three months ended March 31, 2017 as a result of NOD cures and ongoing analysis of recent loss development trends. Reserves of $2.5 million related to prior year defaults remained as of March 31, 2017.

The following tables provide claim development data, by accident year, and a reconciliation to the reserve for insurance claims and claim expenses, related to the new guidance on short-duration contracts.



	Reserves net of Reinsurance										As of March 31, 2017
Accident Year	2013		2014		2015		2016		2017		Total of IBNR		NODs
	($ Values In Thousands)
2013	$	—	$	24	$	—	$	—	$	—	$	—	—
2014			56		34		—		—		—		—
2015					652		614		408		9		9
2016							2,210		1,921		113		107
2017									716		96		91
							Total		$	3,045	$	218	207

Our IBNR reserves reflect the actuarial estimate for claims incurred but not reported as of March 31, 2017. The number of NODs outstanding as of March 31, 2017 is the total number of loans in default over 60 days for which we have established reserves.



	Cumulative Paid Claims, net of Reinsurance
Accident Year	2013		2014		2015		2016		2017
	(In Thousands)
2013	$	—	$	—	$	—	$	—	$	—
2014			—		4		—		—
2015					50		196		105
2016							171		37
2017									—
							Total		$	142



Reconciliation of Disclosure of Incurred and Paid Claims Development to the Liability for Unpaid Claims and Claim Adjustment Expenses
(In Thousands)
	As of March 31, 2017
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	$	3,121
Reinsurance recoverable on unpaid claims	564
Unallocated claims adjustment expenses	76
Total gross liability for unpaid claims and claim adjustment expenses	$	3,761

The below table shows, on average, the percentage of claims paid over the years after a claim is incurred.



	Average annual percentage payout of incurred claims by age, net of reinsurance
	Year 1	Year 2		Year 3		Year 4		Year 5
Claims duration disclosure	3%	11	%	9	%	—	%	—	%

Earnings (Loss) per Share

3 Months Ended

Mar. 31, 2017

Earnings Per Share [Abstract]

Earnings (Loss) per Share

Basic earnings (loss) per share is based on the weighted average number of shares of common stock outstanding, while diluted earnings (loss) per share is based on the weighted average number of shares of common stock outstanding and common stock equivalents that would be issuable upon the exercise of stock options, other share-based compensation arrangements, and the dilutive effect of outstanding warrants. The following table reconciles the net income and the weighted average shares of common stock outstanding used in the computations of basic and diluted earnings (loss) per share of common stock:



	For the three months ended March 31,
	2017		2016
	(In Thousands, except for per share data)
Net income (loss)	$	5,492	$	(3,907	)

Basic earnings (loss) per share	$	0.09	$	(0.07	)

Basic weighted average shares outstanding	59,183,973		58,936,694
Dilutive effect of non-vested shares	3,154,883		—
Dilutive weighted average shares outstanding	62,338,856		58,936,694

Diluted earnings (loss) per share	$	0.09	$	(0.07	)

For the three months ended March 31, 2017, 1,121,471 of our common stock equivalents we issued under share-based compensation arrangements were not included in the calculation of diluted earnings (loss) per share because they were anti-dilutive. Non-vested shares of 3,154,883 were included in our weighted average number of common shares outstanding for the three months ended March 31, 2017.

As a result of our net losses for the three months ended March 31, 2016, 7,351,338 of our common stock equivalents we issued under share-based compensation arrangements and warrants were not included in the calculation of diluted earnings (loss) per share as of such dates because they were anti-dilutive.

Warrants	3 Months Ended
Warrants	Mar. 31, 2017
Debt Disclosure [Abstract]
Warrants	Warrants We issued 992,000 warrants in connection with our Private Placement. 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. Upon exercise of these warrants, the amounts will be treated as additional paid-in capital. No warrants were exercised during the three months ended March 31, 2017 and 2016. We account for these warrants to purchase our common shares in accordance with ASC 470-20, Debt with Conversion and Other Options and ASC 815-40, Derivatives and Hedging - Contracts in Entity's Own Equity.

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes We are a U.S. taxpayer and are subject to a statutory U.S. federal corporate income tax rate of 35%. Our holding company files a consolidated U.S. federal and various state income tax returns on behalf of itself and its subsidiaries. Our provision for income taxes for the interim reporting periods are based on an estimated annual effective tax rate for the year ending December 31, 2017. Our effective tax rate on our pre-tax income was 18.5% for the three months ended March 31, 2017, compared to 0.0% for the comparable 2016 period. The increase in the effective tax expense for the three months ended March 31, 2017, against the comparable 2016 period was attributable to the elimination of tax benefits during the comparable 2016 period due to the recognition of a full valuation allowance which had been recorded to reflect the amount of the deferred taxes that may not be realized. See Item 1, “Financial Statements and Supplementary Data - Notes to Consolidated Financial Statements - Note 1, Organization and Basis of Presentation - Immaterial Correction of Prior Period Amounts” for further details.

Statutory Information

3 Months Ended

Mar. 31, 2017

Insurance [Abstract]

Statutory Information

Our insurance subsidiaries, NMIC and Re One, file financial statements in conformity with statutory basis 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. 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 loss, statutory surplus, contingency reserve and risk-to-capital (RTC) ratios were as follows:



As of and for the three months and year ended	March 31, 2017			December 31, 2016
	(In Thousands)
Statutory net income (loss)	$	(10,090	)	$	(26,653	)
Statutory surplus	404,359			413,809
Contingency reserve	109,198			90,479
Risk-to-Capital	12.4:1			11.6:1

NMIH is not subject to any limitations on its ability to pay dividends except those generally applicable to corporations that are incorporated in Delaware, such as NMIH. Delaware corporation law provides that dividends are only payable out of a corporation's capital surplus or recent net profits (subject to certain limitations). Since inception, NMIC has not paid any dividends to NMIH. As NMIC had a statutory net loss for the year ended December 31, 2016, NMIC cannot pay any dividends to NMIH through December 31, 2017, without the prior approval of the Wisconsin OCI.

Organization and Basis of Presentation (Policies)	3 Months Ended
Organization and Basis of Presentation (Policies)	Mar. 31, 2017
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, 2016, included in our 2016 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. 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, 2017.
Deferred Policy Acquisition Costs	Deferred Policy Acquisition Costs Costs directly associated with the successful acquisition of mortgage insurance policies, consisting of certain selling expenses and other policy issuance and underwriting expenses, are initially deferred and reported as deferred policy acquisition costs (DAC). DAC is reviewed periodically to determine that it does not exceed recoverable amounts and is adjusted as appropriate for policy cancellations to be consistent with our revenue recognition policy. We estimate the rate of amortization to reflect actual experience and any changes to persistency or loss development. For each book year of business, these costs are amortized to expense in proportion to estimated gross profits over the estimated life of the policies.
Premium Deficiency Reserves	Premium Deficiency Reserves We consider whether a premium deficiency exists at each fiscal quarter using best estimate assumptions as of the testing date. Per ASC 944, a premium deficiency reserve shall be recognized if the sum of expected claim costs and claim adjustment expenses, expected dividends to policyholders, unamortized acquisition costs, and maintenance costs exceeds related unearned premiums and anticipated investment income.
Reinsurance	Reinsurance We account for premiums, losses and loss expenses that are ceded to reinsurers on bases consistent with those we use to account for the original policies we issue and pursuant to the terms of our reinsurance contracts. We account for premiums ceded to reinsurers as reductions to premium revenue. We earn profit commissions, which represent a percentage of the profits recognized by the reinsurers that are returned to us, based on the level of losses ceded. We recognize any profit commissions we earn as increases in net premium revenue. We receive ceding commissions, calculated as a percentage of ceded written premiums, which are intended to cover our costs to acquire and service the direct policies. We earn the ceding commissions 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 as reductions to underwriting and operating expenses. We cede a portion of loss reserves, paid losses and loss expenses, which are accounted for as reductions to loss expense and as reinsurance recoverables. We remain directly liable for all loss payments in the event we are unable to collect from any reinsurer.
Premiums Receivable	Premiums Receivable Premiums receivable consist of premiums due on our mortgage insurance policies. If a mortgage insurance premium is unpaid for more than 120 days, the receivable is written off against earned premium and the related insurance policy is canceled.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial accounting Standards Board (the FASB) issued Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers (Topic 606). This update is intended to provide a consistent approach in recognizing revenue. In accordance with the new standard, recognition of revenue occurs when a customer obtains control of promised goods or services in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In addition, the new standard requires that reporting companies disclose the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. In August 2015, ASU 2015-14 deferred the provisions of ASU 2014-09 to be effective for interim and annual periods beginning after December 15, 2017. In addition, this guidance amends the existing requirements for the recognition of a gain or loss on the transfer of non-financial assets that are not in a contract with a customer (ASU 2017-05). The Company is currently evaluating the impact the adoption of this ASU will have, if any, on the consolidated financial statements; however, this update is not expected to impact the recognition of revenue related to insurance premiums or investments, which represent the majority of our total revenues. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). This update requires that businesses recognize rights and obligations associated with certain leases as assets and liabilities on the balance sheet.The standard also requires additional disclosures regarding the amount, timing, and uncertainty of cash flows arising from leases. For public business entities, this update is effective for annual periods beginning after December 15, 2018 and interim periods therein. Early adoption is permitted in any period. We expect to adopt this guidance on January 1, 2019. We anticipate this standard will have a material impact on our financial position, primarily due to our office space operating lease, as we will be required to recognize lease assets and lease liabilities on our consolidated balance sheet. We will continue to assess the potential impacts of this standard, including the impact the adoption of this guidance will have on our results of operations or cash flows. In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326). This update requires companies to measure all expected credit losses for financial assets held at the reporting date. The accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration also is amended in the standard. The standard will take effect for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. The Company is currently in the early stages of evaluating the impact the adoption of this ASU will have, if any, on the consolidated financial statements. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230). This update is intended to reduce diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The standard will take effect for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017. The Company is currently in the early stages of evaluating the impact the adoption of this ASU will have, if any, on the consolidated financial statements. In August 2016, the FASB issued ASU 2016-16, Income Taxes- Intra-Entity Transfers of Assets Other Than Inventory (Topic 740). This update is intended to improve the accounting for the income tax consequences of intra-entity transfers of assets other than inventory. The standard will take effect for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017. Early adoption is permitted at the beginning of any annual reporting period. The Company is currently in the early stages of evaluating the impact the adoption of this ASU will have, if any, on the consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, Intangibles - Goodwill and Other (Topic 350). This update is intended to simplify the test for goodwill impairment. The standard will take effect for public business entities for fiscal years, and interim periods within those fiscal years, after December 15, 2020. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company is currently in the early stages of evaluating the impact the adoption of this ASU will have, if any, on the consolidated financial statements. In March 2017, the FASB issued ASU 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20). This update shortens the amortization period for the premium on certain purchased callable debt securities to the earliest call date. The standard will take effect for public business entities for fiscal years beginning after December 15, 2017. Early adoption is permitted, and if an entity early adopts the guidance in an interim period, any adjustments are reflected as of the beginning of the fiscal year that includes that interim period. The Company is currently in the early stages of evaluating the impact the adoption of this ASU will have, if any, on the consolidated financial statements.
Earnings Per Share	Basic earnings (loss) per share is based on the weighted average number of shares of common stock outstanding, while diluted earnings (loss) per share is based on the weighted average number of shares of common stock outstanding and common stock equivalents that would be issuable upon the exercise of stock options, other share-based compensation arrangements, and the dilutive effect of outstanding warrants.

Organization and Basis of Presentation (Tables)

3 Months Ended

Mar. 31, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Prior Period Adjustments

A comparison of the effected amounts as reported and as adjusted are reported below.



As of and for the full year ended December 31, 2016	As previously reported			As adjusted
	(In thousands)
Income Statement
Net income	$	65,841		$	64,001
Income tax (benefit)	(54,389		)	(52,550		)
Basic EPS	1.11			1.08
Diluted EPS	1.08			1.05

Balance Sheet
Deferred tax asset, net	$	53,274		$	51,434
Total assets	841,737			839,897
Accumulated deficit	(94,882		)	(96,722		)
Total shareholder's equity	477,349			475,509

Investments (Tables)

3 Months Ended

Mar. 31, 2017

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 Cost		Gross Unrealized					Fair Value
	Amortized Cost		Gains		Losses			Fair Value
As of March 31, 2017	(In Thousands)
U.S. Treasury securities and obligations of U.S. government agencies	$	66,555	$	3	$	(850	)	$	65,708
Municipal debt securities	70,543		316		(463		)	70,396
Corporate debt securities	360,955		2,466		(1,781		)	361,640
Asset-backed securities	107,008		696		(313		)	107,391
Total bonds	605,061		3,481		(3,407		)	605,135
Short-term investments	53,402		103		—			53,505
Total investments	$	658,463	$	3,584	$	(3,407	)	$	658,640



	Amortized Cost		Gross Unrealized					Fair Value
	Amortized Cost		Gains		Losses			Fair Value
As of December 31, 2016	(In Thousands)
U.S. Treasury securities and obligations of U.S. government agencies	$	64,135	$	6	$	(962	)	$	63,179
Municipal debt securities	40,801		131		(663		)	40,269
Corporate debt securities	349,712		1,722		(2,356		)	349,078
Asset-backed securities	114,456		765		(560		)	114,661
Total bonds	569,104		2,624		(4,541		)	567,187
Short-term investments	61,584		198		—			61,782
Total investments	$	630,688	$	2,822	$	(4,541	)	$	628,969

Schedule of Investments by Maturity



As of March 31, 2017	Amortized Cost		Fair Value
	(In Thousands)
Due in one year or less	$	120,819	$	120,890
Due after one through five years	147,875		148,565
Due after five through ten years	266,793		266,076
Due after ten years	15,968		15,718
Asset-backed securities	107,008		107,391
Total investments	$	658,463	$	658,640



As of December 31, 2016	Amortized Cost		Fair Value
	(In Thousands)
Due in one year or less	$	94,382	$	94,584
Due after one through five years	173,296		173,251
Due after five through ten years	242,005		240,060
Due after ten years	6,549		6,413
Asset-backed securities	114,456		114,661
Total investments	$	630,688	$	628,969

Schedule of Aging Unrealized Losses

For those securities in an unrealized loss position, the length of time the securities were in such a position is as follows:



	Less Than 12 Months						12 Months or Greater						Total
	# of Securities	Fair Value		Unrealized Losses			# of Securities	Fair Value		Unrealized Losses			# of Securities	Fair Value		Unrealized Losses
As of March 31, 2017		(Dollars in Thousands)
U.S. Treasury securities and obligations of U.S. government agencies	37	$	61,703	$	(850	)	—	$	—	$	—		37	$	61,703	$	(850	)
Municipal debt securities	14	27,663		(431		)	1	1,718		(32		)	15	29,381		(463		)
Corporate debt securities	60	100,085		(1,465		)	6	11,022		(316		)	66	111,107		(1,781		)
Asset-backed securities	23	29,086		(241		)	10	8,547		(72		)	33	37,633		(313		)
Total investments	134	$	218,537	$	(2,987	)	17	$	21,287	$	(420	)	151	$	239,824	$	(3,407	)



	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, 2016		(Dollars in Thousands)
U.S. Treasury securities and obligations of U.S. government agencies	33	$	51,093	$	(962	)	—	$	—	$	—		33	$	51,093	$	(962	)
Municipal debt securities	14	28,659		(617		)	1	1,704		(46		)	15	30,363		(663		)
Corporate debt securities	77	135,115		(1,955		)	8	13,873		(401		)	85	148,988		(2,356		)
Asset-backed securities	30	38,702		(510		)	6	2,472		(50		)	36	41,174		(560		)
Total investments	154	$	253,569	$	(4,044	)	15	$	18,049	$	(497	)	169	$	271,618	$	(4,541	)

Net Investment Income



	For the three months ended March 31,
	2017			2016
	(In Thousands)
Investment income	$	3,993		$	3,408
Investment expenses	(186		)	(178		)
Net investment income	$	3,807		$	3,231

Net Realized Investments Gains (Losses)

Net Realized Investment Gains (Losses)



	For the three months ended March 31,
	2017			2016
	(In Thousands)
Gross realized investment gains	$	279		$	556
Gross realized investment losses	(337		)	(1,441		)
Net realized investment losses	$	(58	)	$	(885	)

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

Fair Value of Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2017

Fair Value Disclosures [Abstract]

Fair Value Measurements, Recurring and Nonrecurring

The following is a list of those assets and liabilities that are measured at fair value by hierarchy level:



	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Fair Value
As of March 31, 2017	(In Thousands)
U.S. Treasury securities and obligations of U.S. government agencies	$	55,746	$	9,962	$	—	$	65,708
Municipal debt securities	—		70,396		—		70,396
Corporate debt securities	—		361,640		—		361,640
Asset-backed securities	—		107,391		—		107,391
Cash, cash equivalents and short-term investments	66,048		—		—		66,048
Total assets	$	121,794	$	549,389	$	—	$	671,183
Warrant liability	—		—		3,563		3,563
Total liabilities	$	—	$	—	$	3,563	$	3,563



	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Fair Value
As of December 31, 2016	(In Thousands)
U.S. Treasury securities and obligations of U.S. government agencies	$	50,719	$	12,460	$	—	$	63,179
Municipal debt securities	—		40,269		—		40,269
Corporate debt securities	—		349,078		—		349,078
Asset-backed securities	—		114,661		—		114,661
Cash, cash equivalents and short-term investments	109,528		—		—		109,528
Total assets	$	160,247	$	516,468	$	—	$	676,715
Warrant liability	—		—		3,367		3,367
Total liabilities	$	—	$	—	$	3,367	$	3,367

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 three months ended March 31,
Warrant Liability	2017		2016
	(In Thousands)
Balance, January 1	$	3,367	$	1,467
Change in fair value of warrant liability included in earnings	196		(670		)
Balance, March 31	$	3,563	$	797

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Term Loan (Tables)

3 Months Ended

Mar. 31, 2017

Debt Disclosure [Abstract]

Schedule of Future Principal Payments

Future principal payments for the Company's Term Loan as of March 31, 2017 are as follows:



As of March 31, 2017	Principal
	(In thousands)
2017	$	1,125
2018	1,500
2019	145,125
Total	$	147,750

Reinsurance (Tables)

3 Months Ended

Mar. 31, 2017

Reinsurance Disclosures [Abstract]

Effects of Reinsurance

The effect of reinsurance on net premiums written and earned is as follows:



	For the three months ended
	March 31, 2017			March 31, 2016
	(In Thousands)
Net premiums written
Direct	$	39,245		$	38,129
Ceded	(4,641		)	—
Net premiums written	$	34,604		$	38,129

Net premiums earned
Direct	$	37,438		$	19,807
Ceded	(4,213		)	—
Net premiums earned	$	33,225		$	19,807

The following tables show the amounts ceded related to the 2016 QSR Transaction:



	For the three months ended
	March 31, 2017			March 31, 2016
	(In Thousands)
Ceded risk-in-force	$	2,167,745		$	—
Ceded premiums written	(4,641		)	—
Ceded premiums earned	(4,213		)	—
Ceding commission written	2,058			—
Ceding commission earned	2,065			—

Reserves for Insurance Claims and Claim Expenses (Tables)

3 Months Ended

Mar. 31, 2017

Insurance [Abstract]

Reconciliation of Liability for Insurance Claims and Claims Expenses

The following table provides a reconciliation of the beginning and ending reserve balances for primary insurance claims and claims expenses:



	For the three months ended March 31,
	2017			2016
	(In Thousands)
Beginning balance	$	3,001		$	679
Less reinsurance recoverables ⁽¹⁾	(297		)	—
Beginning balance, net of reinsurance recoverables	2,704			679

Add claims incurred:
Claims and claim expenses incurred:
Current year ⁽²⁾	955			553
Prior years⁽³⁾	(320		)	(95		)
Total claims and claims expenses incurred	635			458

Less claims paid:
Claims and claim expenses paid:
Current year ⁽²⁾	—			—
Prior years ⁽³⁾	142			—
Total claims and claim expenses paid	142			—

Reserve at end of period, net of reinsurance recoverables	3,197			1,137
Add reinsurance recoverables ⁽¹⁾	564			—
Balance, March 31	$	3,761		$	1,137

⁽²⁾ Related to defaults occurring in the current year.

⁽³⁾ Related to defaults occurring in prior years.

Short-duration Insurance Contracts, Claims Development



	Reserves net of Reinsurance										As of March 31, 2017
Accident Year	2013		2014		2015		2016		2017		Total of IBNR		NODs
	($ Values In Thousands)
2013	$	—	$	24	$	—	$	—	$	—	$	—	—
2014			56		34		—		—		—		—
2015					652		614		408		9		9
2016							2,210		1,921		113		107
2017									716		96		91
							Total		$	3,045	$	218	207



	Cumulative Paid Claims, net of Reinsurance
Accident Year	2013		2014		2015		2016		2017
	(In Thousands)
2013	$	—	$	—	$	—	$	—	$	—
2014			—		4		—		—
2015					50		196		105
2016							171		37
2017									—
							Total		$	142

Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability



Reconciliation of Disclosure of Incurred and Paid Claims Development to the Liability for Unpaid Claims and Claim Adjustment Expenses
(In Thousands)
	As of March 31, 2017
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	$	3,121
Reinsurance recoverable on unpaid claims	564
Unallocated claims adjustment expenses	76
Total gross liability for unpaid claims and claim adjustment expenses	$	3,761

Short-duration Insurance Contracts, Schedule of Historical Claims Duration

The below table shows, on average, the percentage of claims paid over the years after a claim is incurred.



	Average annual percentage payout of incurred claims by age, net of reinsurance
	Year 1	Year 2		Year 3		Year 4		Year 5
Claims duration disclosure	3%	11	%	9	%	—	%	—	%

Earnings (Loss) per Share (Tables)

3 Months Ended

Mar. 31, 2017

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 earnings (loss) per share of common stock:



	For the three months ended March 31,
	2017		2016
	(In Thousands, except for per share data)
Net income (loss)	$	5,492	$	(3,907	)

Basic earnings (loss) per share	$	0.09	$	(0.07	)

Basic weighted average shares outstanding	59,183,973		58,936,694
Dilutive effect of non-vested shares	3,154,883		—
Dilutive weighted average shares outstanding	62,338,856		58,936,694

Diluted earnings (loss) per share	$	0.09	$	(0.07	)

Statutory Information (Tables)

3 Months Ended

Mar. 31, 2017

Insurance [Abstract]

Schedule of Statutory Net Loss, Surplus, Contingency Reserve and Risk-to-Capital Ratio

NMIC and Re One's combined statutory net loss, statutory surplus, contingency reserve and risk-to-capital (RTC) ratios were as follows:



As of and for the three months and year ended	March 31, 2017			December 31, 2016
	(In Thousands)
Statutory net income (loss)	$	(10,090	)	$	(26,653	)
Statutory surplus	404,359			413,809
Contingency reserve	109,198			90,479
Risk-to-Capital	12.4:1			11.6:1

- Definition

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

+ References + Details

Organization and Basis of Presentation (Details)	1 Months Ended		3 Months Ended
Organization and Basis of Presentation (Details)	Nov. 30, 2013 shares	Apr. 30, 2012 USD ($) shares	Mar. 31, 2017 USD ($) state	Mar. 31, 2016 USD ($)
Business Acquisition [Line Items]
Proceeds from issuance of common stock, net of stock issuance costs		$ 510,000,000
Number of states in which the entity operates \| state			50
Deferred policy acquisition cost, amortization expense			$ 1,000,000	$ 900,000
Premium deficiency reserve			$ 0	$ 0
Common Stock - Class A
Business Acquisition [Line Items]
Stock issued during period, shares, net issues (in shares) \| shares		55,000,000
MAC Financial Holding Corporation and Subsidiaries
Business Acquisition [Line Items]
Consideration transferred, cash and equity interests issued and issuable		$ 8,500,000
Consideration transferred, liabilities incurred		$ 1,300,000
IPO
Business Acquisition [Line Items]
Stock issued during period, shares, net issues (in shares) \| shares	2,400,000

Organization and Basis of Presentation - Prior Period Adjustment (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income	$ 5,492	$ (3,907)	$ 64,001
Income tax (benefit)	$ 1,248	$ 0	$ (52,550)
Basic EPS (in dollars per share)	$ 0.09	$ (0.07)	$ 1.08
Diluted EPS (in dollars per share)	$ 0.09	$ (0.07)	$ 1.05
Deferred tax asset, net	$ 50,529		$ 51,434
Total assets	840,162		839,897
Accumulated deficit	(90,716)		(96,722)
Total shareholder's equity	$ 483,909		475,509	$ 402,731
Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income			65,841
Income tax (benefit)			$ (54,389)
Basic EPS (in dollars per share)			$ 1.11
Diluted EPS (in dollars per share)			$ 1.08
Deferred tax asset, net			$ 53,274
Total assets			841,737
Accumulated deficit			(94,882)
Total shareholder's equity			477,349
Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Deferred tax asset, net			$ (1,800)

Organization and Basis of Presentation - Change in Accounting Principle (Details) $ in Thousands	Dec. 31, 2016 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment	$ 514
Retained deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment	514
ASU No. 2016-09 \| Retained deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment	$ 500

Organization and Basis of Presentation - Subsequent Reinsurance Agreement (Details) $ in Millions	May 02, 2017 USD ($)
Subsequent Event \| Oaktown Re Ltd
Subsequent Event [Line Items]
Excess of loss reinsurance agreement	$ 211.3

Investments - Fair Values and Gross Unrealized Gains and Losses on Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 658,463	$ 630,688
Gross Unrealized Gains	3,584	2,822
Gross Unrealized (Losses)	(3,407)	(4,541)
Fair Value	658,640	628,969
U.S. Treasury securities and obligations of U.S. government agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	66,555	64,135
Gross Unrealized Gains	3	6
Gross Unrealized (Losses)	(850)	(962)
Fair Value	65,708	63,179
Municipal debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	70,543	40,801
Gross Unrealized Gains	316	131
Gross Unrealized (Losses)	(463)	(663)
Fair Value	70,396	40,269
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	360,955	349,712
Gross Unrealized Gains	2,466	1,722
Gross Unrealized (Losses)	(1,781)	(2,356)
Fair Value	361,640	349,078
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	107,008	114,456
Gross Unrealized Gains	696	765
Gross Unrealized (Losses)	(313)	(560)
Fair Value	107,391	114,661
Bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	605,061	569,104
Gross Unrealized Gains	3,481	2,624
Gross Unrealized (Losses)	(3,407)	(4,541)
Fair Value	605,135	567,187
Short-term investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	53,402	61,584
Gross Unrealized Gains	103	198
Gross Unrealized (Losses)	0	0
Fair Value	$ 53,505	$ 61,782

Investments - Scheduled Maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Amortized Cost
Due in one year or less	$ 120,819	$ 94,382
Due after one through five years	147,875	173,296
Due after five through ten years	266,793	242,005
Due after ten years	15,968	6,549
Asset-backed securities	107,008	114,456
Amortized Cost	658,463	630,688
Fair Value
Due in one year or less	120,890	94,584
Due after one through five years	148,565	173,251
Due after five through ten years	266,076	240,060
Due after ten years	15,718	6,413
Asset-backed securities	107,391	114,661
Fair Value	$ 658,640	$ 628,969

Investments - Unrealized Losses (Details) $ in Thousands	Mar. 31, 2017 USD ($) security	Dec. 31, 2016 USD ($) security
Schedule of Available-for-sale Securities [Line Items]
Number of securities, less than 12 months \| security	134	154
Fair value, less than 12 months	$ 218,537	$ 253,569
Unrealized losses, less than 12 months	$ (2,987)	$ (4,044)
Number of securities,12 months or greater \| security	17	15
Fair value, 12 months or greater	$ 21,287	$ 18,049
Unrealized losses, 12 months or greater	$ (420)	$ (497)
Number of securities, total \| security	151	169
Fair value	$ 239,824	$ 271,618
Unrealized Losses	$ (3,407)	$ (4,541)
U.S. Treasury securities and obligations of U.S. government agencies
Schedule of Available-for-sale Securities [Line Items]
Number of securities, less than 12 months \| security	37	33
Fair value, less than 12 months	$ 61,703	$ 51,093
Unrealized losses, less than 12 months	$ (850)	$ (962)
Number of securities,12 months or greater \| security	0	0
Fair value, 12 months or greater	$ 0	$ 0
Unrealized losses, 12 months or greater	$ 0	$ 0
Number of securities, total \| security	37	33
Fair value	$ 61,703	$ 51,093
Unrealized Losses	$ (850)	$ (962)
Municipal debt securities
Schedule of Available-for-sale Securities [Line Items]
Number of securities, less than 12 months \| security	14	14
Fair value, less than 12 months	$ 27,663	$ 28,659
Unrealized losses, less than 12 months	$ (431)	$ (617)
Number of securities,12 months or greater \| security	1	1
Fair value, 12 months or greater	$ 1,718	$ 1,704
Unrealized losses, 12 months or greater	$ (32)	$ (46)
Number of securities, total \| security	15	15
Fair value	$ 29,381	$ 30,363
Unrealized Losses	$ (463)	$ (663)
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Number of securities, less than 12 months \| security	60	77
Fair value, less than 12 months	$ 100,085	$ 135,115
Unrealized losses, less than 12 months	$ (1,465)	$ (1,955)
Number of securities,12 months or greater \| security	6	8
Fair value, 12 months or greater	$ 11,022	$ 13,873
Unrealized losses, 12 months or greater	$ (316)	$ (401)
Number of securities, total \| security	66	85
Fair value	$ 111,107	$ 148,988
Unrealized Losses	$ (1,781)	$ (2,356)
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Number of securities, less than 12 months \| security	23	30
Fair value, less than 12 months	$ 29,086	$ 38,702
Unrealized losses, less than 12 months	$ (241)	$ (510)
Number of securities,12 months or greater \| security	10	6
Fair value, 12 months or greater	$ 8,547	$ 2,472
Unrealized losses, 12 months or greater	$ (72)	$ (50)
Number of securities, total \| security	33	36
Fair value	$ 37,633	$ 41,174
Unrealized Losses	$ (313)	$ (560)

Investments - Net Investment Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Investment Income, Net [Abstract]
Investment income	$ 3,993	$ 3,408
Investment expenses	(186)	(178)
Net investment income	$ 3,807	$ 3,231

Investments - Net Realized Investment Gains (Losses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Gross realized investment gains	$ 279	$ 556
Gross realized investment losses	(337)	(1,441)
Net realized investment losses	$ (58)	$ (885)

Investments - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
Investments - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss position, accumulated loss	$ 3,407	$ 4,541
Unrealized losses, 12 months or greater	420	497
Other-than-Temporary-Impairment on investments	144
U.S. Treasury securities and obligations of U.S. government agencies
Schedule of Available-for-sale Securities [Line Items]
Cash and investments held with various state insurance departments	6,900	6,900
Unrealized loss position, accumulated loss	850	962
Unrealized losses, 12 months or greater	$ 0	$ 0

- Definition

Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the customer may deposit additional funds at any time and effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid Investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Short-term investments, exclusive of cash equivalents, generally consist of marketable securities intended to be sold within one year (or the normal operating cycle if longer) and may include trading securities, available-for-sale securities, or held-to-maturity securities (if maturing within one year), as applicable.

+ References + Details

Fair Value of Financial Instruments - Rollforward of Level 3 (Details) - Significant Unobservable Inputs (Level 3) - Warrant Liability - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 3,367	$ 1,467
Change in fair value of warrant liability included in earnings	196	(670)
Ending balance	$ 3,563	$ 797

Fair Value of Financial Instruments - Narrative (Details) - Warrant Liability - Significant Unobservable Inputs (Level 3)	3 Months Ended
	Mar. 31, 2017 $ / shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Share price (in dollars per share)	$ 11.40
Risk free rate	1.70%
Expected term	3 years 11 months
Volatility assumption	30.50%
Expected dividend rate	0.00%

Term Loan - Narrative (Details) - USD ($)			3 Months Ended		15 Months Ended
Term Loan - Narrative (Details) - USD ($)	Feb. 10, 2017	Nov. 10, 2015	Mar. 31, 2017	Mar. 31, 2016	Feb. 10, 2017
Debt Instrument [Line Items]
Term loan			$ 147,750,000
Debt issuance cost			370,000	$ 0
Interest expense			3,494,000	$ 3,632,000
Senior Secured Debt \| Credit Agreement
Debt Instrument [Line Items]
Debt instrument term		3 years
Debt instrument, face amount		$ 150,000,000
Periodic payment of principal			375,000
Term loan			$ 147,800,000
Debt issuance cost	$ 370,000				$ 4,800,000
Percentage of debt discount		1.00%
Debt instrument covenant, maximum debt-to-total capitalization ratio			35.00%
Debt instrument covenant, maximum risk-to-capital ratio			22.0
Debt instrument covenant, minimum liquidity requirement			$ 33,400,000
Senior Secured Debt \| Credit Agreement \| Eurodollar
Debt Instrument [Line Items]
Variable rate floor			1.00%
Basis spread on variable rate			6.75%
Interest rate during period			8.00%

Term Loan - Schedule of Future Principal Payments (Details) $ in Thousands	Mar. 31, 2017 USD ($)
Future Principal Payments [Abstract]
2017	$ 1,125
2018	1,500
2019	145,125
Total	$ 147,750

Reinsurance - Narrative (Details) - USD ($) $ in Thousands	Sep. 01, 2016	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Ceded Credit Risk [Line Items]
Reinsurance recoverable on unpaid claims		$ 564	$ 297	$ 0	$ 0
Third-Party Reinsurers
Ceded Credit Risk [Line Items]
Ceding commissions under 2016 QSR Transaction	20.00%
Threshold for loss ratio on loans under 2016 QSR Transaction to qualify for profit commission	60.00%
Reinsurance recoverable on unpaid claims		$ 564
Existing Risk Written Policies \| Third-Party Reinsurers
Ceded Credit Risk [Line Items]
Percent of policies ceded under 2016 QSR Transaction	25.00%
Fannie Mae \| Third-Party Reinsurers
Ceded Credit Risk [Line Items]
Percent of policies ceded under 2016 QSR Transaction	100.00%
Risk Written Policies from September 1, 2016 through December 31, 2017 \| Third-Party Reinsurers
Ceded Credit Risk [Line Items]
Percent of policies ceded under 2016 QSR Transaction	25.00%

Reinsurance - Effect of Reinsurance on Net Premiums Written and Earned (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Net premiums written
Direct	$ 39,245	$ 38,129
Ceded	(4,641)	0
Net premiums written	34,604	38,129
Net premiums earned
Direct	37,438	19,807
Ceded	(4,213)	0
Net premiums earned	$ 33,225	$ 19,807

Reinsurance - Amounts Ceded Related to 2016 QSR Transaction (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Ceded Credit Risk [Line Items]
Ceded premiums written	$ (4,641)	$ 0
Ceded premiums earned	(4,213)	$ 0
Third-Party Reinsurers
Ceded Credit Risk [Line Items]
Ceded risk-in-force	2,167,745
Ceded premiums written	(4,641)
Ceded premiums earned	(4,213)
Ceding commission written	2,058
Ceding commission earned	$ 2,065

Reserves for Insurance Claims and Claim Expenses - Narrative (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) loan claim	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Liability for Claims and Claims Adjustment Expense [Line Items]
IBNR, default period (at least)	60 days
Total gross liability for unpaid claims and claim adjustment expenses	$ 3,761	$ 1,137	$ 3,001	$ 679
Primary loans in default \| loan	207
Number of claims paid \| claim	4
Claims paid	$ 142	0
Favorable prior year development	320	$ 95
Reserve for prior year insurance claims and claim expenses	$ 2,500
Fannie Mae
Liability for Claims and Claims Adjustment Expense [Line Items]
Number of loans in pool past due 60 days or more \| loan	47
Risk in Force of loans in pool past due 60 days or more	$ 3,100
Deductible on policy	$ 10,100
Loan-to-value ratio (less than)	0.8
Claims applied to pool deductible	$ 256

Reserves for Insurance Claims and Claim Expenses - Reconciliation of Reserve Balances for Insurance Claims Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning balance	$ 3,001	$ 679
Less reinsurance recoverables	297	0
Beginning balance, net of reinsurance recoverables	2,704	679
Claims incurred:
Current year	955	553
Prior years	(320)	(95)
Total claims and claims expenses incurred	635	458
Claims and claim expenses paid:
Current year	0	0
Prior years	142	0
Total claims and claim expenses paid	142	0
Ending balance, net of reinsurance recoverables	3,197	1,137
Add reinsurance recoverables	564	0
Reserve at end of period, net of reinsurance recoverables	$ 3,761	$ 1,137

Reserves for Insurance Claims and Claim Expenses - Claim Development by Accident Year and Reconciliation of Reserve for Insurance Claims and Claims Expense (Details) - Financial Guarantee Insurance Product Line $ in Thousands	Mar. 31, 2017 USD ($) claim	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Claims Development [Line Items]
Reserves net of Reinsurance	$ 3,045
Incurred but not reported claims liability	$ 218
Cumulative number of reported claims \| claim	207
Cumulative Paid Claims, net of Reinsurance	$ 142
2013
Claims Development [Line Items]
Reserves net of Reinsurance	0	$ 0	$ 0	$ 24	$ 0
Incurred but not reported claims liability	$ 0
Cumulative number of reported claims \| claim	0
Cumulative Paid Claims, net of Reinsurance	$ 0	0	0	0	$ 0
2014
Claims Development [Line Items]
Reserves net of Reinsurance	0	0	34	56
Incurred but not reported claims liability	$ 0
Cumulative number of reported claims \| claim	0
Cumulative Paid Claims, net of Reinsurance	$ 0	0	4	$ 0
2015
Claims Development [Line Items]
Reserves net of Reinsurance	408	614	652
Incurred but not reported claims liability	$ 9
Cumulative number of reported claims \| claim	9
Cumulative Paid Claims, net of Reinsurance	$ 105	196	$ 50
2016
Claims Development [Line Items]
Reserves net of Reinsurance	1,921	2,210
Incurred but not reported claims liability	$ 113
Cumulative number of reported claims \| claim	107
Cumulative Paid Claims, net of Reinsurance	$ 37	$ 171
2017
Claims Development [Line Items]
Reserves net of Reinsurance	716
Incurred but not reported claims liability	$ 96
Cumulative number of reported claims \| claim	91
Cumulative Paid Claims, net of Reinsurance	$ 0

Reserves for Insurance Claims and Claim Expenses - Reconciliation of Disclosure of Incurred and Paid Claims Development to the Liability for Unpaid Claims and Claims Adjustment Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Reinsurance recoverable on unpaid claims	$ 564	$ 297	$ 0	$ 0
Total gross liability for unpaid claims and claim adjustment expenses	3,761	$ 3,001	$ 1,137	$ 679
Financial Guarantee Insurance Product Line
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	3,121
Reinsurance recoverable on unpaid claims	564
Unallocated claims adjustment expenses	76
Total gross liability for unpaid claims and claim adjustment expenses	$ 3,761

Reserves for Insurance Claims and Claim Expenses - Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance (Details) - Financial Guarantee Insurance Product Line	Mar. 31, 2017
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	3.00%
Year 2	11.00%
Year 3	9.00%
Year 4	0.00%
Year 5	0.00%

Earnings (Loss) per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Earnings Per Share [Abstract]
Net income (loss)	$ 5,492	$ (3,907)	$ 64,001
Basic earnings (loss) per share (in dollars per share)	$ 0.09	$ (0.07)	$ 1.08
Basic weighted average shares outstanding (in shares)	59,183,973	58,936,694
Dilutive effect of non-vested shares (in shares)	3,154,883	0
Dilutive weighted average shares outstanding (in shares)	62,338,856	58,936,694
Diluted earnings (loss) per share (in dollars per share)	$ 0.09	$ (0.07)	$ 1.05

Earnings (Loss) per Share - Narrative (Details) - shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive effect of non-vested shares (in shares)	3,154,883	0
Stock Compensation Plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from EPS calculation (in shares)	1,121,471
Stock Compensation Plan and Warrant
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from EPS calculation (in shares)		7,351,338

Warrants (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Apr. 30, 2012
Debt Disclosure [Abstract]
Warrants issued (in shares)			992,000
Right to purchase, number of shares per warrant			1
Exercise price of warrants (in dollars per warrant)			$ 10.00
Warrants value			$ 5.1
Number of warrants exercised during period	0	0

Income Taxes - Narrative (Details)	3 Months Ended
Income Taxes - Narrative (Details)	Mar. 31, 2017	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	35.00%
Effective income tax rate on pre-tax income or loss	18.50%	0.00%

Statutory Information - Schedule of Statutory Net Loss, Surplus, Contingency Reserve and Risk-to-Capital Ratio (Details) - Combined $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Statutory Accounting Practices [Line Items]
Statutory net income (loss)	$ (10,090)	$ (26,653)
Statutory surplus	404,359	413,809
Contingency reserve	$ 109,198	$ 90,479
Risk-to-Capital	12.4	11.6

Fair Value of Financial Instruments - Assets and Liabilities at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 658,640	$ 628,969
Warrant liability	3,563	3,367
U.S. Treasury securities and obligations of U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	65,708	63,179
Municipal debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	70,396	40,269
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	361,640	349,078
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	107,391	114,661
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash, cash equivalents and short-term investments	66,048	109,528
Total assets	671,183	676,715
Warrant liability	3,563	3,367
Total liabilities	3,563	3,367
Fair Value, Measurements, 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]
Available-for-sale securities	65,708	63,179
Fair Value, Measurements, Recurring \| Municipal debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	70,396	40,269
Fair Value, Measurements, Recurring \| Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	361,640	349,078
Fair Value, Measurements, Recurring \| Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	107,391	114,661
Fair Value, Measurements, 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	66,048	109,528
Total assets	121,794	160,247
Warrant liability	0	0
Total liabilities	0	0
Fair Value, Measurements, 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]
Available-for-sale securities	55,746	50,719
Fair Value, Measurements, 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]
Available-for-sale securities	0	0
Fair Value, Measurements, 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]
Available-for-sale securities	0	0
Fair Value, Measurements, 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]
Available-for-sale securities	0	0
Fair Value, Measurements, 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	549,389	516,468
Warrant liability	0	0
Total liabilities	0	0
Fair Value, Measurements, 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]
Available-for-sale securities	9,962	12,460
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Municipal debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	70,396	40,269
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	361,640	349,078
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	107,391	114,661
Fair Value, Measurements, 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	3,563	3,367
Total liabilities	3,563	3,367
Fair Value, Measurements, 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]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Municipal debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 0	$ 0