NMI (NMIH) 10-K 12 Mar 14 2013 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2013	Mar. 07, 2014	Jun. 30, 2013
Document and Entity Information [Abstract]	'	'	'
Entity Registrant Name	'NMI HOLDINGS, INC.	'	'
Entity Central Index Key	'0001547903	'	'
Document Type	'10-K	'	'
Document Period End Date	31-Dec-13	'	'
Amendment Flag	'false	'	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'
Current Fiscal Year End Date	'--12-31	'	'
Entity Well-known Seasoned Issuer	'No	'	'
Entity Voluntary Filers	'No	'	'
Entity Current Reporting Status	'Yes	'	'
Entity Filer Category	'Non-accelerated Filer	'	'
Entity Public Float	'	'	$0
Entity Common Stock, Shares Outstanding	'	58,065,326	'

CONSOLIDATED_BALANCE_SHEETS

CONSOLIDATED BALANCE SHEETS (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Investments, available-for-sale, at fair value:	'	'
Fixed maturities (amortized cost of $416,135 and $0 as of December 31, 2013 and December 31, 2012, respectively)	$409,088	$0
Short-term investments	0	4,864
Total investments	409,088	4,864
Cash and cash equivalents	55,929	485,855
Accrued investment income	2,001	6
Prepaid expenses	1,519	417
Restricted cash	0	40,338
Deferred policy acquisition costs, net	90	0
Goodwill and other indefinite lived intangible assets	3,634	3,634
Software and equipment, net	8,876	7,550
Premiums receivable	19	0
Other assets	63	104
Total Assets	481,219	542,768
Liabilities	'	'
Unearned premiums	1,446	0
Reserve for insurance claims and claims expenses	0	0
Accounts payable and accrued expenses	10,052	8,707
Placement fee payable	0	38,305
Purchase consideration payable	0	2,033
Warrant liability, at fair value	6,371	4,842
Deferred tax liability	133	133
Total Liabilities	18,002	54,020
Commitments and Contingencies	'	'
Shareholders' Equity	'	'
Additional paid-in capital	553,707	517,032
Accumulated other comprehensive (loss) income	-7,047	1
Accumulated deficit	-84,024	-28,840
Total Shareholders' Equity	463,217	488,748
Total Liabilities and Shareholders' Equity	481,219	542,768
Common Class A [Member]	'	'
Shareholders' Equity	'	'
Common stock, shares outstanding	581	553
Common Class B [Member]	'	'
Shareholders' Equity	'	'
Common stock, shares outstanding	$0	$2

CONSOLIDATED_BALANCE_SHEETS_Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified
Fixed maturity, amortized cost	$416,135	$0
Common Class A [Member]	'	'
Common stock, par value (in dollars per share)	$0.01	$0.01
Common stock, shares issued	58,052,480	55,250,100
Common stock, shares outstanding	58,052,480	55,250,100
Common stock, shares authorized	250,000,000	250,000,000
Common Class B [Member]	'	'
Common stock, par value (in dollars per share)	$0.01	$0.01
Common stock, shares issued	0	250,000
Common stock, shares outstanding	0	250,000
Common stock, shares authorized	250,000	250,000

CONSOLIDATED_STATEMENTS_OF_COM

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (USD $)	7 Months Ended	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2013		Dec. 31, 2012
Premiums written	'	'		'
Direct	$0	$3,541		$0
Net premiums written	0	3,541		0
Increase in unearned premium	0	-1,446		0
Net premiums earned	0	2,095		0
Net investment income	0	4,808		6
Net realized investment gains	0	186		0
(Loss) Gain from change in fair value of warrant liability	0	-1,529		278
Total Revenues	0	5,560		284
Expenses	'	'		'
Insurance claims and claims expenses	0	0		0
Amortization of deferred policy acquisition costs	0	1		0
Other underwriting and operating expenses	1,349	60,743		27,775
Total Expenses	1,349	60,744		27,775
Net Loss	-1,349	-55,184		-27,491
Other Comprehensive (Loss) Income (net of tax)	'	'		'
Net unrealized holding (losses) gains for the period included in accumulated other comprehensive (loss) income	0	-7,047		1
Other Comprehensive (Loss) Income (net of tax)	0	-7,047		1
Total Comprehensive Loss	($1,349)	($62,231)		($27,490)
Loss per share	'	'		'
Basic and Diluted loss per share (in dollars per share)	($13,490)	($0.99)	[1]	($0.73)	[1]
Weighted average common shares outstanding (in shares)	100	56,005,326	[1]	37,909,936	[1]
[1]	Due to the use of weighted average shares outstanding when calculating earnings per share, the sum of quarterly per share data may not equal the per share data for the year.

CONSOLIDATED_STATEMENTS_OF_SHA

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (USD $)	Total	Common Class A [Member]	Common Class B [Member]	Common Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
				Common Class A [Member]	Common Class B [Member]		Common Class A [Member]
Beginning Balance at Dec. 31, 2010	'	'	'	'	'	'	'	'	'
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'	'	'	'	'	'	'	'	'
Issuance of shares of common stock, shares	'	'	'	55,000,000	250,000	'	'	'	'
Issuance of shares of common stock	'	$508,970,000	$2,000	$551,000	$2,000	'	$508,419,000	'	'
Issuance of common stock related to acquisition of subsidiaries, shares	'	'	'	250,000	'	'	'	'	'
Issuance of common stock related to acquisition of subsidiaries	2,500,000	'	'	2,000	'	2,498,000	'	'	'
Share-based compensation expense	6,115,000	'	'	'	'	6,115,000	'	'	'
Change in unrealized investment gains/losses	1,000	'	'	'	'	'	'	1,000	'
Net loss	-27,491,000	'	'	'	'	'	'	'	'
Ending Balance at Dec. 31, 2011	-1,349,000	'	'	0	0	0	'	0	-1,349,000
Ending Balance, shares at Dec. 31, 2011	'	'	'	0	0	'	'	'	'
Beginning Balance at May. 18, 2011	0	'	'	0	0	0	'	0	0
Beginning Balance, shares at May. 18, 2011	'	'	'	0	0	'	'	'	'
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'	'	'	'	'	'	'	'	'
Issuance of shares of common stock, shares	'	'	'	100	'	'	'	'	'
Issuance of shares of common stock	'	1	'	0.01	'	'	'	'	'
Net loss	-1,349,000	'	'	'	'	'	'	'	'
Ending Balance at Dec. 31, 2011	-1,349,000	'	'	0	'	'	'	'	-1,349,000
Ending Balance, shares at Dec. 31, 2011	'	'	'	0	'	'	'	'	'
Beginning Balance at Dec. 31, 2012	488,748,000	'	'	553,000	2,000	517,032,000	'	1,000	-28,840,000
Beginning Balance, shares at Dec. 31, 2012	'	55,250,100	250,000	55,250,000	250,000	'	'	'	'
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'	'	'	'	'	'	'	'	'
Issuance of Class A shares of common stock related to restricted stock units, shares	'	'	'	137,000	'	'	'	'	'
Issuance of Class A shares of common stock related to restricted stock units	'	-1,578,000	'	1,000	'	'	-1,579,000	'	'
Issuance of shares of common stock, shares	'	'	'	2,415,000	'	'	'	'	'
Issuance of shares of common stock	'	27,912,000	'	25,000	'	'	27,887,000	'	'
Conversion of Class B shares of common stock into Class A shares of common stock, shares	'	'	'	250,000	-250,000	'	'	'	'
Conversion of Class B shares of common stock into Class A shares of common stock	'	'	'	2,000	-2,000	'	'	'	'
Share-based compensation expense	10,367,000	'	'	'	'	10,367,000	'	'	'
Change in unrealized investment gains/losses	-7,048,000	'	'	'	'	'	'	-7,048,000	'
Net loss	-55,184,000	'	'	'	'	'	'	'	-55,184,000
Ending Balance at Dec. 31, 2013	$463,217,000	'	'	$581,000	$0	$553,707,000	'	($7,047,000)	($84,024,000)
Ending Balance, shares at Dec. 31, 2013	'	58,052,480	0	58,052,000	0	'	'	'	'

CONSOLIDATED_STATEMENTS_OF_SHA1

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - (Parenthetical) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013
Payments of stock issuance costs	$3,483

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	7 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2012
Net Cash Provided by (Used in) Operating Activities [Abstract]	'	'	'
Net loss	($1,349)	($55,184)	($27,491)
Adjustments to reconcile net loss to net cash used in operating activities:	'	'	'
Share-based compensation expense	0	10,367	6,115
Warrants issued in connection with line of credit	0	0	1,620
Loss (gain) from change in fair value of warrant liability	0	1,529	-278
Net realized investment gains	0	-186	0
Loss on impairment	0	0	1,200
Depreciation and other amortization	0	8,116	3
Changes in operating assets and liabilities:	'	'	'
Accrued investment income	0	-2,001	-6
Unearned premiums	0	1,446	0
Prepaid expenses	-183	-1,102	-234
Deferred policy acquisition costs, net	0	-90	0
Premiums receivable	0	-19	0
Other assets	-27	46	-78
Accounts payable and accrued expenses	1,354	767	4,553
Net Cash Used in Operating Activities	-205	-36,311	-14,596
Cash Flows from Investing Activities	'	'	'
Purchase of short-term investments	0	-510	-4,862
Purchase of fixed maturities, available-for-sale	0	-559,875	0
Proceeds from maturity of short-term investments	0	5,374	0
Proceeds from sale of fixed maturities, available-for-sale	0	141,754	0
Purchase of software and equipment	0	-6,692	-2,447
Acquisition of subsidiaries	0	0	-2,500
Net Cash Used in Investing Activities	0	-419,949	-9,809
Cash Flows from Financing Activities	'	'	'
(Payments) Proceeds on line of credit	205	0	-205
Taxes paid related to net share settlement of equity awards	0	-1,578	0
Issuance of common stock	0	27,912	510,465
Net Cash Provided by Financing Activities	205	26,334	510,260
Net (Decrease) Increase in Cash and Cash Equivalents	0	-429,926	485,855
Cash and Cash Equivalents, beginning of period	0	485,855	0
Cash and Cash Equivalents, end of period	0	55,929	485,855
Supplemental Disclosures of Cash Flow Information	'	'	'
Restricted Cash	0	0	40,338
Noncash Financing Activities	'	'	'
Conversion of Class B shares of common stock into Class A shares of common stock	$0	$2	$0
Acquisition of subsidiaries	'	'	'
Warrants issued in connection with acquisition of subsidiaries, shares	0	0	3,500
Common stock issued in connection with acquisition of subsidiaries, shares	0	0	2,500

Organization_and_Basis_of_Pres

Organization and Basis of Presentation	12 Months Ended
	Dec. 31, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Organization and Basis of Presentation	'
	Organization and Basis of Presentation
	NMI Holdings, Inc. ("NMIH"), a Delaware corporation, was formed in May 2011 with the intention of providing private mortgage guaranty insurance through a wholly owned insurance subsidiary. From May 2011 through March 2013, our activities were limited to raising capital, seeking to acquire the assets and approvals necessary to become a private mortgage guaranty insurance provider and hiring personnel. The accompanying consolidated financial statements include the accounts of NMI Holdings, Inc. and its wholly owned subsidiaries, MAC Financial Holding Corporation, National Mortgage Insurance Corporation ("NMIC"), previously named Mortgage Assurance Corporation, National Mortgage Reinsurance Inc One ("Re One"), previously named Mortgage Assurance Reinsurance Inc One, and National Mortgage Reinsurance Inc Two ("Re Two"), previously named Mortgage Assurance Reinsurance Inc Two. In April 2013, we, through our primary insurance subsidiary, wrote our first mortgage guaranty insurance policy. On September 30, 2013, we merged Re Two into NMIC with NMIC surviving the merger and MAC Financial Holding Corporation merged into NMI Holdings, Inc., with NMI Holdings, Inc. surviving the merger.
	On November 30, 2011, we entered into an agreement with MAC Financial Ltd. to acquire MAC Financial Holding Corporation and its subsidiaries, Mortgage Assurance Corporation, Mortgage Assurance Reinsurance Inc One and Mortgage Assurance Reinsurance Inc Two, for $8.5 million in cash, common stock and warrants plus the assumption of $1.3 million in liabilities . In addition, we incurred $0.1 million in tax liabilities as a result of the acquisition of certain indefinite-lived intangibles. The MAC Acquisition was completed in April 2012.
	In April 2012, we offered and sold 55.0 million shares of common stock at an issue price of $10.00 per share in our Private Placement. Gross proceeds from the Private Placement were $550.0 million. Net proceeds from the Private Placement, after an approximate 7% underwriting fee and other offering expenses, were approximately $510 million. The fee was escrowed for the benefit of FBR Capital Markets and Co. ("FBR") and was released to FBR upon our receipt of approval from Federal National Home Mortgage Association ("Fannie Mae") and Federal Home Loan Mortgage Corporation ("Freddie Mac") ("GSE Approval").
	Under the terms of the Private Placement, we had until January 17, 2013 to obtain GSE Approval ("GSE Approval Deadline"). NMIC was approved as an eligible mortgage guaranty insurer by Freddie Mac and Fannie Mae, on January 15, 2013 and January 16, 2013, respectively, which approvals are conditioned upon NMIC maintaining certain conditions. For a further discussion of these conditions, see "Note 9, Commitments and Contingencies."
	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 on November 8, 2013, under the symbol “NMIH.” For a further discussion see "Note 3, Common Stock Offerings."
	Basis of Presentation
	The accompanying consolidated financial statements include the results of NMIH and its wholly owned subsidiaries. All intercompany transactions have been eliminated. These financial statements have been prepared in accordance with GAAP and our accounts are maintained in US dollars. The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect reported amounts of assets and liabilities, as well as disclosure of contingent assets and liabilities as of the balance sheet date. Estimates also affect the reported amounts of income and expenses for the reporting period. Actual results could differ from those estimates.
	Basic net loss per share is based on the weighted-average number of common shares outstanding, while diluted net loss per share is based on the weighted-average number of common shares outstanding and common stock equivalents that would be issuable upon the exercise of stock options, other stock-based compensation arrangements, and the dilutive effect of outstanding warrants. As a result of our net losses for the years ended December 31, 2013 and December 31, 2012, 5,303,394 and 4,414,165 shares of our common stock equivalents issued under stock-based compensation arrangements and warrants, respectively, were not included in the calculation of diluted net loss per share as of such dates because they were anti-dilutive.

Summary_of_Accounting_Policies

Summary of Accounting Policies	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Summary of Accounting Principles	'
	Summary of Accounting Principles
	Cash and Cash Equivalents
	We consider items such as certificates of deposit and money market funds with original maturities of 90 days or less to be cash equivalents.
	There was no restricted cash as of December 31, 2013; however, we had restricted cash as of December 31, 2012. The restricted cash balance was comprised of two escrow accounts that were initially funded on April 24, 2012, in connection with our Private Placement, with an agreement that the funds would be released to FBR and MAC Financial Ltd. upon GSE Approval. On January 23, 2013, after receipt of GSE approval, the restricted cash was released from escrow.
	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 (loss) income in shareholders' equity. Net realized investment gains and losses are reported in income based upon specific identification of securities sold.
	Purchases and sales of investments are recorded on a trade date basis. Net investment income is recognized when earned and includes interest and dividend income together with amortization of market premiums and discounts using the effective yield method and is net of investment management fees and other investment related expenses. For asset-backed securities and any other holdings for which there is a prepayment risk, prepayment assumptions are evaluated and revised as necessary. Any adjustments required due to the change in effective yields and maturities are recognized on a prospective basis through yield adjustments.
	Each quarter we evaluate our investments in order to determine whether declines in fair value below amortized cost were considered other-than-temporary in accordance with applicable guidance. In evaluating whether a decline in fair value is other-than-temporary, we consider several factors including, but not limited to:
	•	our intent to sell the security or whether it is more likely than not that we will be required to sell the security before recovery;
	•	severity and duration of the decline in fair value;
	•	the financial condition of the issuer;
	•	the failure of the issuer to make scheduled interest or principal payments;
	•	recent credit downgrades of the applicable security or the issuer below investment grade; and
	•	adverse conditions specifically related to the security, an industry, or a geographic area.
	Under the current guidance, a debt security impairment is deemed other than temporary if (i) we either intend to sell the security, or it is more likely than not that we will be required to sell the security before recovery or (ii) we do not expect to collect cash flows sufficient to recover the amortized cost basis of the security. In the event of the decline in fair value of a debt security, a holder of that security that does not intend to sell the debt security and for whom it is more likely than not that such holder will be required to sell the debt security before recovery of its amortized cost basis is required to separate the decline in fair value into (a) the amount representing the credit loss and (b) the amount related to other factors. The amount of total decline in fair value related to the credit loss shall be recognized in earnings as OTTI with the amount related to other factors recognized in accumulated other comprehensive income or loss, net of tax. In periods after recognition of an OTTI on debt securities, we account for such securities as if they had been purchased on the measurement date of the OTTI at an amortized cost basis equal to the previous amortized cost basis less the OTTI recognized in earnings. For debt securities for which OTTI were recognized in earnings, the difference between the new amortized cost basis and the cash flows expected to be collected will be accreted into net investment income. The determination of OTTI is a subjective process, and different judgments and assumptions could affect the timing of the loss realization.
	Revenue Recognition
	In the mortgage guaranty insurance industry, a “book” is a group of loans that an MI company insures in a particular period, normally a calendar year. We set premiums at the time a policy is issued based on our expectations regarding likely performance over the term of coverage. The policies we write are guaranteed renewable contracts at the policyholder's option on a single, annual or monthly premium basis. We generally have no ability to re-underwrite or reprice these contracts. However, we review every loan and through this review process confirm underwriting eligibility, either prior to loan closing in the non-delegated channel or through a post-closing underwriting review in the delegated channel. Based on this review, we may re-price. Premiums written on a single premium basis and an annual premium basis are initially deferred as unearned premium reserve and earned over the policy term.  Premiums written on policies covering more than one year are amortized over the policy life in accordance with the expiration of risk which is the anticipated claim payment pattern based on industry experience.  Premiums written on annual policies are earned on a monthly pro rata basis.  Premiums written on monthly policies are earned as coverage is provided. Premiums written on pool transactions are earned over the period that coverage is provided.  Upon cancellation of a policy, all premium that is non-refundable is immediately earned. Any refundable premium is returned to the policyholder. Premiums returned to policyholders are recorded as a reduction of written and earned premiums in the current period. The actual return of premium for all periods affects premiums written and earned in those periods.
	For the year ended December 31, 2013, one insured represented 97% of our NIW. At December 31, 2013, approximately 28% of our IIF was concentrated in California. We commenced mortgage guaranty insurance operations in April of 2013. As such, our insurance-in-force and customer concentrations are not representative of those concentrations that will exist when our insurance portfolio is more mature. Furthermore, given the relatively small size of the portfolio, small concentrations can appear to be larger than normal.
	Deferred Policy Acquisition Costs
	Costs directly associated with the successful acquisition of mortgage guaranty 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"). For each book year of business, these costs are amortized to income in proportion to estimated gross profits over the estimated life of the policies.
	Business Combinations, Goodwill and Intangible Assets
	Goodwill represents the excess of the purchase price over the estimated fair value of net assets acquired from a business combination. In accordance with ASC 350, Intangibles - Goodwill and Other, we test goodwill for impairment during the third quarter each year or more frequently if we believe indicators of impairment exist. We have not identified any impairments of goodwill through December 31, 2013.
	Our intangible assets consist of state licenses and GSE applications which have indefinite lives. We test indefinite-lived intangible assets for impairment during the fourth quarter of each year or more frequently if we believe indicators of impairment exist. We do not believe that the indefinite-lived intangible assets were impaired as of December 31, 2013.
	Software and Equipment
	Software and equipment are stated at cost, less accumulated amortization and depreciation. Amortization and depreciation are calculated using the straight-line method over the estimated useful lives of the respective assets ranging typically from 3 to 7 years, unless factors indicate a shorter useful life. Amortization of software and depreciation of equipment commences at the beginning of the month following the placement of the assets into use by us. We have reduced the useful life of our insurance management system. For further detail see "Note 7, Software and Equipment."
	Warrants
	We account for warrants to purchase our common shares in accordance with ASC 470-20 Debt with Conversion and Other Options and ASC 815-40 Derivatives and Hedging - Contracts in Entity's Own Equity. Our outstanding warrants, issued to FBR and former stockholders of MAC Financial Ltd., may be settled by us using either (i) physical settlement method or (ii) cashless exercise, where shares that are issued upon exercise of the warrants are reduced, to cover the cost of the exercise, in lieu of the holder remitting a cash payment of the exercise price. The warrants expire and are not exercisable on the 10th anniversary after the date the warrant was issued. The exercise price and the number of warrants are subject to anti-dilution provisions whereby the existing exercise price is adjusted downward, and the number of warrants increased, for events that may not be dilutive. The adjustment may be in excess of any dilution suffered. As a result, the warrants are classified as a liability. We revalue the warrants at the end of each reporting period and any change in fair value is reported in the statements of operations in the period in which the change occurred. The fair value of the warrants is calculated using a Black-Scholes option-pricing model in combination with a binomial model and a Monte Carlo simulation model used to value the pricing protection features within the warrant.
	Share-Based Compensation
	We account for stock compensation in accordance with ASC 718, Compensation - Stock Compensation. This addresses accounting for share-based awards and recognition of compensation expense, measured using grant date fair value, over the requisite service or performance period of the award. Share-based payments include RSUs and stock option grants under the 2012 Stock Incentive Plan. The fair value of stock option grants issued are determined based on an option pricing model which takes into account various assumptions that are subjective. Key assumptions used in the stock option valuation include the expected term of the equity award taking into account the contractual term of the award, the effects of expected exercise and post-vesting termination behavior, expected volatility, expected dividends and the risk-free interest rate for the expected term of the award. RSU grants to employees contain a market condition and/or service condition. The fair value of RSU grants to employees with a market condition is determined based on a Monte Carlo simulation model at the date of grant. RSU grants to employees with a service condition and RSU grants to non-employee directors are valued at our stock price on the date of grant less the present value of anticipated dividends.
	Offering and Incorporation Expenses
	Offering expenses incurred in connection with our capitalization were recorded as a reduction of paid-in-capital at closing. These costs include certain investment banking fees, legal fees, printer fees and audit fees. Any incorporation and organizational expenses not related to the raising of capital are expensed as incurred and are included in the statement of operations.
	Reserve for Insurance Claims and Claims Expenses
	We establish 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 claims reserves only for loans in default. We are a new company and have only recently commenced transacting mortgage guaranty insurance. We have not received any primary NODs, and thus have not established any primary reserves for claims or IBNR for the years ended December 31, 2013, 2012 or 2011. Additionally, we entered into a pool insurance transaction with Fannie Mae, effective September 1, 2013. For this pool transaction, any claims reserve potentially established would be in excess of the transaction's deductible, which represents the amount payable by Fannie Mae on initial claims. The consideration of the deductible would serve to delay the recording of any claim reserve until estimated claims exceed the deductible amount. In addition, all of the loans in the pool have LTVs below 80%. As a result, the potential for any one default to result in a loss to the insured is mitigated. We have not established any pool reserves for claims or IBNR for the years ended December 31, 2013, 2012 or 2011. See "Note 9, Commitments and Contingencies", for more information on this pool transaction.
	Premium Deficiency Reserves
	After our insurance claim reserves are established, we will perform a premium deficiency calculation 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. Because we have not established any reserves, as discussed above, we have also determined that no premium deficiency reserves were necessary for the years ended December 31, 2013, 2012 or 2011.
	Income Taxes
	We account for income taxes using the liability method in accordance with ASC 740 - Income Taxes. The liability method measures the expected future tax effects of temporary differences at the enacted tax rates applicable for the period in which the deferred asset or liability is expected to be realized or settled. Temporary differences are differences between the tax basis of an asset or liability and its reported amount in the consolidated financial statements that will result in future increases or decreases in taxes owed on a cash basis compared to amounts already recognized as tax expense in the consolidated statement of operations.
	We evaluate the need for a valuation allowance against our deferred tax assets on a quarterly basis. In the course of our review, we assess all available evidence, both positive and negative, including future sources of income, tax planning strategies, future contractual cash flows and reversing temporary differences. Additional valuation allowance benefits or charges could be recognized in the future due to changes in our expectation regarding the realization of tax benefits. Uncertain tax positions taken or expected to be taken in a tax return by us are recognized in the financial statements when it is more likely than not that the position would be sustained upon examination by tax authorities. There are no tax uncertainties that are expected to result in significant increases or decreases to unrecognized tax benefits within the next twelve month period.
	In assessing the valuation of deferred tax assets, we consider whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible.
	Recent Accounting Standards Updates Adopted
	Clarifying the Scope of Disclosures about Offsetting Assets and Liabilities
	In January 2013, the FASB issued an Accounting Standards Update clarifying that the scope of Update 2011-11, Balance Sheet (Topic 210): Disclosures about Offsetting Assets and Liabilities, applies to derivatives accounted for in accordance with Topic 815, Derivatives and Hedging, including bifurcated embedded derivatives, repurchase agreements and reverse repurchase agreements, and securities borrowing and securities lending transactions that are either offset in accordance with Section 210-20-45 or Section 815-10-45 or subject to an enforceable master netting arrangement or similar agreement. The amendments are effective for fiscal years beginning on or after January 1, 2013, and interim periods within those annual periods. The adoption of this guidance in January 2013 did not have any effect on our results of operations, financial position or liquidity.
	Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income
	In February 2013, the FASB issued an Accounting Standards Update addressing the reporting of reclassifications out of accumulated other comprehensive income. The Update requires an entity to report the effect of significant reclassifications out of accumulated other comprehensive income on the respective line items in the statement of operations if the amount being reclassified is required under GAAP to be reclassified in its entirety to net income. For other amounts that are not required under GAAP to be reclassified in their entirety to net income in the same reporting period, an entity is required to cross-reference other disclosures required under GAAP that provide additional detail about those amounts. The adoption of this guidance in December 2013 did not have any impact on our results of operations, financial position or liquidity.
	Reclassifications
	Certain items in the financial statements as of December 31, 2012 and for the periods ending December 31, 2012 and December 31, 2011 have been reclassified to conform to the current period's presentation. There was no effect on net income or shareholders' equity previously reported.
	Subsequent Events
	On January 24, 2014, NMIC's principal regulator declined to disapprove of the faculative pool excess share reinsurance agreement with Re One, which was effective September 1, 2013.
	On January 30, 2014, Arch announced the closing of its acquisition of CMG and certain assets of PMI. The terms of the February 7, 2013 Asset Purchase Agreement ("APA") between Arch and PMI provide that effective as of the closing of that transaction, PMI shall transfer and assign to Arch all causes of action being pursued by PMI in the PMI Complaint. The APA further provides that within thirty (30) days after the closing of the transaction, Arch shall have its attorney file appropriate pleadings and other documents and instruments with the court requesting that PMI be removed as a party plaintiff in the PMI Complaint and that Arch be substituted as the real party in interest. Although Arch has not yet filed any such request with the Court, the plaintiff is now described in pleadings as “Plaintiff and Real Party in Interest Arch U.S. MI Services, Inc.”
	We have considered subsequent events through the date of this filing.

Common_Stock_Offering

Common Stock Offering	12 Months Ended
	Dec. 31, 2013
Equity [Abstract]	'
Common Stock Offering	'
	Common Stock Offerings
	We entered into a purchase/placement agreement with FBR on April 17, 2012 and offered and sold an aggregate of 55,000,000 of our Class A common shares resulting in net proceeds of approximately $510 million. In accordance with the terms of the Private Placement, we placed approximately 93% (or $476 million) of our net proceeds from this Private Placement into investment accounts established for the purpose of preserving such proceeds, on a short-term basis, prior to approval from at least one of the GSEs, as an eligible mortgage guaranty insurance provider to the GSE. As provided in our certificate of incorporation, this amount was not to be disbursed (used for operating activities) until the earlier of (i) receipt by us of GSE Approval or (ii) our liquidation. Approximately $35 million of the net proceeds were available for paying the cash portion of the MAC Acquisition and to pay off the FBR line of credit. The remaining balance of approximately $32 million was placed in an operating account for the purpose of funding our operations through the time of GSE Approval.
	The initial purchaser's discount and placement fee of $38.3 million was comprised of $19.5 million in common stock and $18.8 million in cash. On October 24, 2012, FBR sold the aforementioned common stock and proceeds of $19.5 million were retained in an escrow account until we received GSE Approval.
	In January 2013, following GSE Approval, the escrow funds were released and distributed to FBR (its initial purchasers' discount and placement fees from the escrow account) and to MAC (its cash portion of the MAC Acquisition), respectively.
	On November 8, 2013, we filed a final prospectus announcing the sale of 2.1 million shares of common stock through an initial public offering. The underwriters of the offering were granted a 30-day option to purchase up to an additional 315,000 shares of common stock from us at an initial public offering price of $13.00, less underwriting discounts and commissions, to cover over-allotments. The principal reason for conducting the public offering was to expedite an increase in the number of holders of our common stock to permit a listing of our common stock on the NASDAQ. Obtaining a listing on the NASDAQ satisfied certain contractual obligations we had to our stockholders under a Registration Rights Agreement.
	On November 12, 2013, the underwriters exercised their option in full to purchase an additional 315,000 shares of common stock at a price of $13.00 per share, before underwriting discounts. The offering closed on November 14, 2013. Gross proceeds to us were $31.4 million. Net proceeds from the offering were approximately $28 million, after an approximate 6% underwriting fee and other offering expenses and reimbursements pursuant to the underwriting agreement.

Acquisition_of_MAC

Acquisition of MAC	12 Months Ended
	Dec. 31, 2013
Business Combinations [Abstract]	'
Acquisition of MAC	'
	Acquisition of MAC
	On November 30, 2011, we entered into a definitive stock purchase agreement with MAC Financial Ltd. to acquire MAC Financial Holdings Corporation and its wholly owned subsidiaries (collectively "MAC"). The transaction closed shortly after the closing of the common stock Private Placement described above. Under the agreement, the total initial consideration paid for MAC was $8.5 million consisting of $2.5 million in cash, $2.5 million in our common stock, and warrants to acquire our common stock valued at $3.5 million. The consideration (net of expenses paid on MAC's behalf) was held in an escrow account until we received GSE Approval, upon which time it was released to MAC Financial Ltd. The total purchase consideration was allocated to the acquired assets and liabilities as follows:
	April 24, 2012	(In Thousands)
	Current assets	$	52
	Intangibles	1,590
	Capitalized software	5,000
	Goodwill	3,244
	Subtotal	9,886
	Current liabilities and deferred tax liabilities	(1,386		)
	Estimated fair value of net assets acquired	$	8,500
	Pursuant to the terms of the stock purchase agreement, we assumed $1.3 million of MAC's existing liabilities, which related to outstanding payment obligations under its vendor contracts with CDW, LLC, Milliman, Inc., and Intellect/SEEC, Inc. and incurred $0.1 million in tax liabilities as a result of the acquisition of certain indefinite-lived intangibles. All other liabilities which existed at closing were the sole obligation of MAC Financial Ltd. As of December 31, 2013 and December 31, 2012, the total amount of cash held in escrow (net of expenses paid on MAC's behalf) was $0 and $2.0 million, respectively.
	Included in the acquired intangibles of $1.6 million are operational manuals valued at $1.2 million which at the time of acquisition, were a key deliverable in our GSE application and were expected to be placed in service following GSE Approval. Subsequently, the processes and procedures underlying the operational manuals were reengineered to be substantially different as defined by our current management. Therefore, at December 31, 2012, we determined the carrying value of operational manuals would not be recovered and the manuals could not be sold and would be disposed of, and as a result, we assessed the fair value at zero and recognized a loss on impairment of $1.2 million in the fourth quarter of 2012.

Investments

Investments	12 Months Ended
	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]	'
Investments	'
	Investments
	Fair Values and Gross Unrealized Gains and Losses on Investments
		Amortized				Gross Unrealized							Fair
		Cost				Gains			(Losses)				Value
	As of December 31, 2013	(In Thousands)
	U.S. Treasury securities and obligations of U.S. government agencies	$	108,067			$	—		$	(1,461	)		$	106,606
	Municipal bonds	12,017				1			(85		)		11,933
	Corporate debt securities	221,899				157			(4,799		)		217,257
	Asset-backed securities	74,152				114			(974		)		73,292
	Total bonds	416,135				272			(7,319		)		409,088
	Short-term investments	39,695				—			—				39,695
	Total Investments	$	455,830			$	272		$	(7,319	)		$	448,783
		Amortized				Gross Unrealized							Fair
		Cost				Gains			(Losses)				Value
	As of December 31, 2012	(In Thousands)
	Short-term investments	$	4,863			$	1		$	—			$	4,864
	Total Investments	$	4,863			$	1		$	—			$	4,864
	Scheduled Maturities as of December 31, 2013
	The amortized cost and fair values of available for sale securities at December 31, 2013, 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.
		Amortized				Fair
		Cost				Value
		(In Thousands)
	Due in one year or less	$	—			$	—
	Due after one through five years	260,855				257,501
	Due after five through ten years	65,687				63,440
	Due after ten years	15,441				14,855
	Asset-backed securities	74,152				73,292
	Total Bonds	$	416,135			$	409,088
	All investments held at December 31, 2012 had a scheduled maturity of one year or less. The Company held no investments at December 31, 2011.
	Net Realized Investment Gains (Losses) on Investments
		For the Year Ended December 31, 2013
		(In Thousands)
	Corporate Bond	$	323
	U.S. Treasury securities and obligations of U.S. government agencies	(87		)
	Mortgage-backed security	(50		)
	Total Net Realized Investment Gains	$	186
	There were no realized investment gains or losses for the years ended December 31, 2012 and 2011.
	Aging of Unrealized Losses
	At December 31, 2013, the investment portfolio had gross unrealized losses of approximately $7 million. We did not consider these securities to be other-than-temporarily impaired as of December 31, 2013. We based our conclusion on the following facts (i) the unrealized losses were generally caused by interest rate or credit spread movements since the purchase date; (ii) we did not intend to sell these investments and; (iii) we did not believe that it was more likely than not that we will be required to sell these investments before recovery of our amortized cost basis, which may be at maturity; therefore, we did not consider these investments to be other-than-temporarily impaired at December 31, 2013. 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
		Fair Value			Unrealized Losses			Fair Value			Unrealized Losses				Fair Value		Unrealized Losses
	As of December 31, 2013	(In Thousands)
	U.S. Treasury securities and obligations of U.S. government agencies	$	106,606		$	(1,461	)	$	—		$	—			$	106,606	$	(1,461	)
	Municipal bonds	4,915			(85		)	—			—				4,915		(85		)
	Corporate debt securities	187,714			(4,799		)	—			—				187,714		(4,799		)
	Assets-backed securities	58,225			(974		)	—			—				58,225		(974		)
	Total Bonds	$	357,460		$	(7,319	)	$	—		$	—			$	357,460	$	(7,319	)
	At December 31, 2012, the investment portfolio had no unrealized losses.
	Net investment income is comprised of the following:
		For the Year Ended December 31, 2013				For the Year Ended December 31, 2012			For the Period May 19, 2011 (inception) to December 31, 2011
		(In Thousands)
	Fixed maturities	$	5,289			$	4		$	—
	Cash equivalents	—				2			—
	Other	2				—			—
	Investment income	5,291				6			—
	Investment expenses	(483		)		—			—
	Net Investment Income	$	4,808			$	6		$	—
	As of December 31, 2013 and December 31, 2012, there were approximately $7 million and $5 million, respectively, of cash and investments in the form of U.S. Treasury securities on deposit with various state insurance departments to satisfy regulatory requirements.

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2013
Fair Value Disclosures [Abstract]	'
Fair Value of Financial Instruments	'
	Fair Value of Financial Instruments
	The following describes the valuation techniques used by us to determine the fair value of financial instruments held at December 31, 2013 and December 31, 2012:
	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;
	Level 2 - Prices or valuations based on observable inputs other than quoted prices in active markets for identical assets and liabilities; 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.
	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.
	Liabilities classified as Level 3
	The warrants outstanding are valued using a Black-Scholes option-pricing model in combination with a binomial model and Monte Carlo simulation used to value the pricing protection features within the warrants. Variables in the model include the risk-free rate of return, dividend yield, expected life and expected volatility of our stock price. We assess any potential value associated with pricing protection features using internal models and management estimation.
	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 as of December 31, 2013 and December 31, 2012:
		Fair Value Measurements Using
	Assets and Liabilities at Fair Value	Quoted Prices in		Significant Other		Significant		Fair Value
		Active Markets for		Observable Inputs		Unobservable
		Identical Assets		(Level 2)		Inputs
		(Level 1)				(Level 3)
	As of December 31, 2013	(In Thousands)
	U.S. Treasury securities and obligations of U.S. government agencies	$	49,484	$	57,122	$	—	$	106,606
	Municipal bonds	—		11,933		—		11,933
	Corporate debt securities	—		217,257		—		217,257
	Asset-backed securities	—		73,292		—		73,292
	Cash and cash equivalents	55,929		—		—		55,929
	Total Assets	$	105,413	$	359,604	$	—	$	465,017
	Warrant liability	—		—		$	6,371	$	6,371
	Total Liabilities	$	—	$	—	$	6,371	$	6,371
		Fair Value Measurements Using
	Assets and Liabilities at Fair Value	Quoted Prices in		Significant Other		Significant		Fair Value
		Active Markets for		Observable Inputs		Unobservable
		Identical Assets		(Level 2)		Inputs
		(Level 1)				(Level 3)
	As of December 31, 2012	(In Thousands)
	U.S. Treasury securities and obligations of U.S. government agencies	$	4,864	$	—	$	—	$	4,864
	Cash and cash equivalents	526,194		—		—		526,194
	Total Assets	$	531,058	$	—	$	—	$	531,058
	Warrant liability	—		—		$	4,842	$	4,842
	Total Liabilities	$	—	$	—	$	4,842	$	4,842
	The following is a roll-forward of Level 3 liabilities measured at fair value for the year ended December 31, 2013:
		Warrant Liability
	Year Ended December 31, 2013	(In Thousands)
	Level 3 Instruments Only
	Balance, January 1, 2013	$	4,842
	Change in fair value of warrant liability included in earnings	1,529
	Balance, December 31, 2013	$	6,371
	The fair value of the warrants issued to FBR and MAC Financial Ltd. was estimated on the date of grant using the Black-Scholes option-pricing model, including consideration of any potential additional value associated with pricing protection features. The volatility assumption used, 39.0%, was derived from the historical volatility of the share price of a range of publicly-traded companies with similar types of business to that of ours. No allowance was made for any potential illiquidity associated with the private trading of our shares. We revalue the warrant liability quarterly using a Black-Scholes option-pricing model in combination with a binomial model and a Monte-Carlo simulation model used to value the pricing protection features within the warrant. As of December 31, 2013 the assumptions used in the option pricing model were as follows: a common stock price as of December 31, 2013 of $12.73, risk free interest rate of 2.25%, expected life of 6.58 years and a dividend yield of 0%.
	The carrying value of other selected assets on our consolidated balance sheet approximates fair value.

Software_and_Equipment

Software and Equipment	12 Months Ended
	Dec. 31, 2013
Property, Plant and Equipment [Abstract]	'
Software and Equipment	'
	Software and Equipment
	Software and equipment consist largely of capitalized software purchased in connection with the MAC Acquisition which had a fair value of $5.0 million at the date of acquisition. Software and equipment, net of accumulated amortization and depreciation, as of December 31, consist of the following:
		2013			2012
		(In Thousands)
	Software	$	14,140		$	7,268
	Equipment	542			285
	Leasehold improvements	141			—
	Less accumulated amortization and depreciation	(5,947		)	(3		)
	Software and equipment, net	$	8,876		$	7,550
	Amortization and depreciation expense for the years ended December 31, 2013 and 2012 was $5.9 million and $3,000, respectively.
	In connection with the MAC Acquisition in April 2012, we purchased an insurance management system. Given the time required to upgrade the underwriting module of the system, we made the business decision during the second quarter of 2013 to pursue the development of a new module to support (i) policy servicing and billing and (ii) default and claims management within a new insurance management system. We refer to this new insurance management platform as "AXIS", of which this new module is a component. The new policy servicing, billing and default and claims management module was deployed for production use in November 2013.
	Additionally, during the fourth quarter of 2013, in order to reduce future operating costs, improve operational efficiencies and achieve a more flexible and enhanced user experience for loan originators, we decided to further enhance our underwriting module. The new design and development of this underwriting module started in late 2013 with deployment expected to occur in the fourth quarter of 2014. We have invested and will continue to invest resources to develop AXIS to support our MI operations.
	As a result of the above changes, we were required to reduce the useful life of the purchased insurance management system and shorten the amortization period of the modules. Reducing the useful life of this system has the effect of shortening the amortization period, causing us to record the same amount of amortization expense over a shorter period of time, which was implemented in the second quarter of 2013 and will continue to amortize over the coming quarters. The modules will be completely amortized by November 2014.

Intangible_Assets_and_Goodwill

Intangible Assets and Goodwill	12 Months Ended
	Dec. 31, 2013
Goodwill and Intangible Assets Disclosure [Abstract]	'
Intangible Assets and Goodwill	'
	Intangible Assets and Goodwill
	Intangible assets and goodwill consist of identifiable intangible assets and goodwill purchased in connection with the MAC Acquisition. Intangible assets and goodwill, net, as of December 31, 2013 and December 31, 2012, consist of the following:
	As of December 31, 2013 and December 31, 2012	(In Thousands)		Expected Lives
	Goodwill	$	3,244	Indefinite
	State licenses	260		Indefinite
	GSE approvals	130		Indefinite
	Total Intangible Assets and Goodwill	$	3,634
	We test goodwill and intangibles for impairment in the third and fourth quarter, respectively, of every year, or more frequently if we believe indicators of impairment exist. At the time of the MAC Acquisition, we, as part of the acquisition, acquired operational manuals that were a key deliverable in our GSE application and were expected to be placed in service following GSE Approval. Subsequently, the processes and procedures underlying the operational manuals were reengineered to be substantially different as defined by our current management. Therefore, at December 31, 2012 we determined the carrying value of operational manuals would not be recovered and the manuals could not be sold and would be disposed, and as a result, assessed the fair value at zero and recognized a loss on impairment of $1.2 million. No impairments of indefinite-lived intangibles were identified as of December 31, 2013.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	Commitments and Contingencies
	GSE Approvals
	Fannie Mae and Freddie Mac have imposed certain capitalization, operational and reporting conditions in connection with their approvals of NMIC as a qualified mortgage guaranty insurer. Some of these conditions remain in effect for a three (3) year period from the date of GSE Approval while others do not expressly expire. These conditions require, among other things, that NMIC:
	•	be initially capitalized in the amount of $200 million and that its affiliate reinsurance companies, Re One and Re Two, be initially capitalized in the amount of $10 million each (as of September 30, 2013, Re Two was merged into NMIC, with NMIC surviving the merger. See "Note 1. Organization");
	•	maintain minimum capital of $150 million;
	•	operate at a risk-to-capital ratio not to exceed 15:1 for its first three (3) years and then pursuant to the GSE Eligibility Requirements then in effect;
	•	not declare or pay dividends to affiliates or to NMIH for its first three (3) years, then pursuant to the Eligibility Requirements;
	•	not enter into capital support agreements or guarantees for the benefit of, or purchase or otherwise invest in the debt of, affiliates without the prior written approval of the GSEs for its first three (3) years, then pursuant to the Eligibility Requirements;
	•	not enter into reinsurance or other risk share arrangements without the GSEs' prior written approval for its first three (3) years, then pursuant to the Eligibility Requirements; and
	•	at the direction of one or both of the GSEs, re-domicile from Wisconsin to another state.
	The conditional approvals also include certain additional conditions, limitations and reporting requirements that we anticipate will be included in the GSEs' final Eligibility Requirements, such as limits on costs allocated to NMIC under affiliate expense sharing arrangements, risk concentration, rates of return, requirements to obtain a financial strength rating, provision of ancillary services (i.e., non-insurance) to customers, transfers of underwriting to affiliates, notification requirements regarding change of ownership and new five percent (5%) shareholders, provisions regarding underwriting policies and claims processing as well as certain other obligations.
	Fannie Mae Pool Transaction
	NMIC entered into an agreement (effective coverage date of September 1, 2013) with Fannie Mae, pursuant to which NMIC insures a pool of approximately 22,000 loans with insurance-in-force of approximately $5.2 billion. In September 2013, NMIC received the first premium payment from Fannie Mae. The agreement has an expected term of 10 years from the coverage effective date.
	The pool risk-in-force to NMIC, as of September 1, 2013 was $93.1 million which represents the amount between a deductible payable by Fannie Mae on initial losses and a stop loss, above which, losses are borne by Fannie Mae. NMIC provides this same level of risk coverage over the term of the agreement. The pool agreement obligates NMIC to maintain the greater of (i) the risk-to-capital requirements outlined in the January 2013 approval letter, or (ii) a risk-to-capital ratio of 18:1 on primary business plus statutory capital equal to the amount of net risk-in-force of the pool.
	In addition to the conditions noted above, NMIC, entered into risk-to-capital agreements with certain state insurance regulators. See "Note 14, Statutory Financial Information."
	Office Lease
	We entered into an office facility lease effective July 1, 2012 for a term of two years. In October 2013, we amended our facility’s lease to (i) add 23,000 square feet of furnished office space, and (ii) extend the facility’s lease period through October 31, 2017.
	Management expects that, in the normal course of business, as of December 31, 2013, future minimum lease payments under this lease will be as follows:
	Years ending December 31,	(In Thousands)
	2014	$	1,570
	2015	1,670
	2016	1,741
	2017	1,489
	Totals	$	6,470
	We incurred rent expense, related to this lease, of $0.8 million for the year ended December 31, 2013. Rent expense for the year ended December 31, 2012 was $0.2 million.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2013
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Income Taxes
	Following is a reconciliation of our net deferred income tax asset as of December 31, 2013 and December 31, 2012:
		December 31, 2013
		Gross				Tax Effected
	Deferred tax asset:	(In Thousands)
	Capitalized start-up costs	$	2,579			$	903
	Stock compensation	14,701				5,990
	Unrealized loss on investments	7,047				2,694
	Net operating loss carry forwards	65,276				24,602
	Other	10,118				3,760
	Total gross deferred tax assets	99,721				37,949
	Less: valuation allowance	(94,497		)		(35,778		)
	Total deferred tax assets	5,224				2,171
	Deferred tax liability:
	Capitalized software	(5,008		)		(2,095		)
	Intangible assets	(390		)		(133		)
	Other	(216		)		(76		)
	Total deferred tax liabilities	(5,614		)		(2,304		)
	Net deferred income tax liability	$	(390	)		$	(133	)
		December 31, 2012
		Gross				Tax Effected
	Deferred tax asset:	(In Thousands)
	Capitalized start-up costs	$	21,796			$	7,411
	Net operating loss carry forwards	7,307				2,484
	Total gross deferred tax assets	29,103				9,895
	Less: valuation allowance	(24,103		)		(8,195		)
	Total deferred tax assets	5,000				1,700
	Deferred tax liability:
	Capitalized software	(5,000		)		(1,700		)
	Intangible assets	(390		)		(133		)
	Total deferred tax liabilities	(5,390		)		(1,833		)
	Net deferred income tax liability	$	(390	)		$	(133	)
	At December 31, 2013 and December 31, 2012, we have a net deferred tax liability of $0.1 million as a result of the acquisition of indefinite-lived intangibles in the MAC Acquisition for which no benefit has been reflected in the acquired net operating loss carry forwards. The tax liability incurred at the acquisition is recorded as an increase in Goodwill.
	Excluded from deferred tax assets as of December 31, 2013 is $1.5 million of excess stock compensation for which any benefit realized will be recorded to stockholders' equity.
	As of December 31, 2013, the Company had federal net operating loss carryforwards of $65.3 million, which expire from 2029 to 2033 and state net operating loss carryforwards of $30.5 million, which expire from 2032 to 2033. Section 382 of the Internal Revenue Code imposes annual limitations on a corporation's ability to utilize its net operating loss carryforwards if it experiences an "ownership change." As a result of the MAC Acquisition, $7.3 million of NOLs are subject to annual limitations of $0.8 million through 2016, then $0.3 million through 2029.
	As we have just recently begun insurance operations and have no history to provide a basis for reliable future net income projections, a valuation allowance of $35.8 million and $8.2 million was recorded at December 31, 2013 and December 31, 2012, respectively, to reflect the amount of the deferred tax asset that may not be realized.
	Reconciliation of the federal statutory income tax (benefit) rate to the effective income tax (benefit) rate is as follows:
		Year Ended December 31, 2013			For the Year Ended December 31, 2012
	Federal statutory income tax rate	35	%		35	%
	Loss on impairment	—			(1.48	)
	Prior year adjustment	3.52			1.66
	Other	1.66			(1.00	)
	Valuation allowance	(40.18	)		(28.00	)
	Purchase accounting adjustment	—			(6.18	)
	Effective income tax rate	—	%		—	%
	As of December 31, 2013 and 2012, we have no reserve for unrecognized tax benefits, and have taken no material uncertain positions in its tax returns that would require measurement and recognition.
	We file income tax returns with the U.S. federal government and various state jurisdictions which are subject to potential examination by tax authorities. We are not currently under examination, and federal and state tax years remain open by statute.

ShareBased_Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Share-Based Compensation	'
	Share-Based Compensation
	The 2012 Stock Incentive Plan (the "Plan") was approved by the Board on April 16, 2012, and authorized 5.5 million shares be reserved for issuance under the Plan with 3.85 million shares available for stock options and 1.65 million shares available for RSUs. Options granted under the Plan are Non-Qualified Stock Options and may be granted to employees, directors and other key persons. The exercise price per share for the common stock covered by this Plan shall be determined by the Board at the time of grant, but shall not be less than the fair market value on the date of the grant. The term of the stock option grants will be established by the Board, but no stock option shall be exercisable more than 10 years after the date the stock option is granted. The vesting period of the stock option grants will also be established by the Board at the time of grant and generally is for a three year period. Upon the exercise of stock options, we issue shares from the authorized, unissued share reserve.
	A summary of option activity in the plan during the years ending December 31, 2013 and December 31, 2012 is as follows:
	Option Activity	Shares		Weighted Average Exercise Price		Weighted Average Grant Date Fair Value per Share
		(Shares in Thousands)
	Options balance outstanding at December 31, 2012	2,547		$	10	$	3.86
	Options granted	532		11.78		4.57
	Less: Options forfeited	(15	)	10		3.84
	Less: Options canceled	(1	)	10		3.84
	Options balance outstanding at December 31, 2013	3,063		$	10.31	$	3.98
	Option Activity	Shares		Weighted Average Exercise Price		Weighted Average Grant Date Fair Value per Share
		(Shares in Thousands)
	Options balance outstanding at December 31, 2011	—		$	—	$	—
	Options granted	2,829		10		3.87
	Less: Options forfeited	(282	)	10		3.88
	Less: Options canceled	—		—		—
	Options balance outstanding at December 31, 2012	2,547		$	10	$	3.86
	As of December 31, 2013 there were no exercises and approximately 743,000 options were fully vested and exercisable. The weighted average exercise price for the fully vested and exercisable options was $10.00. The remaining weighted average contractual life of options fully vested and exercisable as of December 31, 2013 was 8.4 years. The aggregate intrinsic value for fully vested and exercisable options was $2.0 million as of December 31, 2013.
	The remaining weighted average contractual life of options outstanding as of December 31, 2013 was 8.5 years. As of December 31, 2013, there was $3.6 million of total unrecognized compensation cost related to non-vested stock options. The weighted-average period over which total compensation related to non-vested stock options will be recognized is 0.72 years.
	We account for stock options under ASC 718, which requires all share-based payments to be recognized in the financial statements at their fair values. To measure the fair value of stock options granted, we utilize the Black-Scholes options pricing model. Expense is recognized over the required service period, which is generally the three-year vesting period of the options (vesting in one-third increments per year).
	The estimated grant date fair values of the stock options granted during 2013 and 2012 were calculated using the Black-Scholes valuation model based on the following assumptions:
		2013		2012
	Expected life	6 years		6 years
	Risk free interest rate	0.98% - 1.12%		0.85% - 1.12%
	Dividend yield	0	%	0	%
	Expected stock price volatility	39	%	39	%
	Projected forfeiture rate	1	%	1	%
	Expected Life - is the period of time over which the options granted are expected to remain outstanding giving consideration to vesting schedules, historical exercise and forfeiture patterns. We use the simplified method outlined in SEC Staff Accounting Bulletin No. 107 to estimate expected lives for options granted during the period as historical exercise data is not available and the options meet the requirements set out in the Bulletin. Options granted have a maximum term of ten years.
	Risk-Free Interest Rate - is the U.S. Treasury rate for the date of the grant having a term approximating the expected life of the option.
	Dividend Yield - is calculated by dividing the expected annual dividend by our stock price at the valuation date.
	Expected Price Volatility - is a measure of the amount by which a price has fluctuated or is expected to fluctuate. At the time of grant, our common shares trading history was not sufficient to calculate an expected volatility representative of the volatility over the expected lives of the options. As a substitute for such estimate, we used historical volatilities of a set of comparable companies in the industry in which we operate.
	Projected Forfeiture Rate - is the estimated percentage of options granted that are expected to be forfeited or canceled before becoming fully vested. An increase in the forfeiture rate will decrease compensation expense.
	A summary of RSU activity in the plan during the years ending December 31, 2013 and December 31, 2012 is as follows:
		Shares		Weighted Average Grant Date Fair Value per Share
		(Shares in Thousands)
	Non-vested restricted stock units at December 31, 2012	1,429		$	7.35
	Restricted stock units granted	76		12.03
	Less: Restricted stock units vested	(263	)	6.79
	Less: Restricted stock units forfeited	—		—
	Non-vested restricted stock units at December 31, 2013	1,242		$	7.75
		Shares		Weighted Average Grant Date Fair Value per Share
		(Shares in Thousands)
	Non-vested restricted stock units at December 31, 2011	—		$	—
	Restricted stock units granted	1,667		7.35
	Less: Restricted stock units forfeited	(238	)	7.35
	Non-vested restricted stock units at December 31, 2012	1,429		$	7.35
	In February 2013, the Board approved a modification to the vesting terms of approximately 400,000 granted and non-vested RSUs held by our employees. The modification to the vesting terms removed the market condition leaving the RSUs subject to a service condition only. The modification resulted in a change in the period over which compensation costs are recognized and prospective recognition of incremental compensation cost. Incremental compensation cost is measured as the excess of the fair value of the modified award over the fair value of the original award immediately before its terms are modified using relevant valuation inputs as of the modification date.
	At December 31, 2013, the 1.2 million shares of granted and non-vested RSUs consisted of 0.5 million shares that are subject to both a market and service condition and 0.7 million shares that are subject only to service conditions. The non-vested RSUs subject to both a market and service condition vest in one-half increments upon the achievement of certain market price goals and continued service. Non-vested RSUs subject only to a service condition vest over a service period ranging from 1 to 3 years. The fair value of RSUs subject to market and service conditions is determined based on a Monte Carlo simulation model at the date of grant. The fair value of RSUs subject only to service conditions are valued at our stock price on the date of grant less the present value of anticipated dividends.
	The estimated grant date fair values of the RSUs granted in 2012 that are subject to both a market and service condition were calculated using a Monte Carlo simulation model based on the average outcome of 150,000 simulations using the following assumption:
	Expected life	5 years
	Risk free interest rate	0.86	%
	Dividend yield	0	%
	Expected stock price volatility	39	%
	Projected forfeiture rate	1	%
	The remaining weighted average contractual life of non-vested RSUs as of December 31, 2013 was 4.0 years. As of December 31, 2013, there was $4.3 million of total unrecognized compensation cost related to non-vested RSUs. The weighted-average period over which total compensation related to non-vested RSUs will be recognized is 0.77 years.
	On April 5, 2013 approximately 263,000 RSUs containing a market condition vested resulting in an acceleration of compensation expense of $1.1 million in the second quarter of 2013.

Warrants

Warrants	12 Months Ended
	Dec. 31, 2013
Debt Disclosure [Abstract]	'
Warrants	'
	Warrants
	As of December 31, 2011, prior to our Private Placement, FBR granted an uncommitted line of credit up to an aggregate principal amount of $1.5 million to support legal, accounting and others costs associated with the formation and our capitalization.
	As part of the consideration for granting the line of credit, upon successful completion of the common stock Private Placement on April 24, 2012, we issued warrants to FBR having an aggregate value equal to three times the amount of the outstanding line of credit balance. Each warrant gave the holder thereof the right to purchase one share of common stock at an exercise price equal to $10.00. Accordingly, FBR was issued approximately 314,000 warrants with an aggregate fair value of $1.6 million which approximated three times the outstanding line of credit amount at that time. These warrants were measured at fair value and recorded as a finance fee with an offsetting charge to liabilities. As the line of credit was paid off on April 24, 2012, the debt discount was fully amortized as of April 24, 2012.
	In addition, in conjunction with the MAC Acquisition, we issued approximately 678,000 warrants to the stockholders of MAC Financial Ltd. at an exercise price equal to $10.00 and an aggregate fair value of $3.5 million. Those stockholders have wound up their affairs pursuant to a members voluntary liquidation under Bermuda law. The shares of our common stock and the warrants previously held by MAC Financial Ltd. have been divided and distributed to its former stockholders.
	Upon exercise of these warrants, the amounts will be reclassified from warrant liability to additional paid-in capital. For the year ended December 31, 2013 all issued warrants are outstanding.
	We account for these warrants to purchase common shares of ours 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. For more detail on how we account for all warrants see "Note 2, Summary of Accounting Principles - Warrants."

Litigation

Litigation	12 Months Ended
	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Litigation	'
	Litigation
	On August 8, 2012, Germaine Marks, as Receiver, and Truitte Todd, as Special Deputy Receiver, of PMI Mortgage Insurance Co. (“PMI”), an Arizona insurance company in receivership, filed a complaint (the “PMI Complaint”) against NMIH, NMIC and certain named individuals, in California Superior Court, Alameda County. The PMI Complaint, as amended, alleges breach of fiduciary duty, breach of loyalty, aiding and abetting breach of fiduciary duty and loyalty, misappropriation of trade secrets, conversion, breach of proprietary information agreement, breach of separation agreement, intentional interference with contractual relations and unfair competition. The lawsuit seeks injunctive relief as well as unspecified monetary damages. We have filed answers to PMI's complaint denying all allegations and believe the claims are without merit. See "Note 2, Summary of Accounting Principles, Subsequent Events."
	The parties are now engaged in discovery and the court has set a trial date for September 29, 2014. Because the litigation and related discovery are ongoing, we do not have sufficient information to determine or predict the ultimate outcome or estimate the range of possible losses, if any. Accordingly, no provision for litigation losses has been included in the financial statements.

Statutory_Information

Statutory Information	12 Months Ended
	Dec. 31, 2013
Insurance [Abstract]	'
Statutory Information	'
	Statutory Information
	Our insurance subsidiaries, NMIC, Re One and Re Two, file financial statements in conformity with statutory basis accounting principles ("SAP") prescribed or permitted by the Wisconsin OCI. Prescribed SAP includes state laws, regulations and general administrative rules, as well as a variety of publications of the National Association of Insurance Commissioners ("NAIC"). The Wisconsin OCI recognizes only statutory accounting practices prescribed or permitted by the state of Wisconsin for determining and reporting the financial condition and results of operations of an insurance company and for determining its solvency under Wisconsin insurance laws. As of September 30, 2013, Re Two was merged into NMIC, with NMIC surviving the merger. See "Note 1, Organization."
	Prescribed and permitted practices generally vary in some respects from accounting principles found in GAAP. The principal differences between these accounting practices and GAAP are as follows: (1) acquisition expenses incurred in connection with acquiring new business are charged to expense under SAP but under GAAP are deferred and amortized as the related premiums are earned; (2) under SAP there are limitations on the net deferred tax assets created by the tax effects of temporary differences; (3) under SAP unpaid claims and claim expenses ceded to reinsurers are reported as a deduction of the related reserve rather than as an asset as would be required under GAAP; (4) under SAP, fixed maturity investments are generally valued at amortized cost while under GAAP, those investments are considered to be available-for-sale and are recorded at fair value, with the unrealized gain or loss recognized, net of tax, as an increase or decrease to shareholders' equity.
	NMIC and Re One's combined statutory net income, statutory surplus and contingency reserve as of and for the years ended December 31, 2012 , 2011 and 2010 were as follows:
		December 31,
		2013			2012			2011
		(In Thousands)
	Statutory net loss	$	(33,307	)	$	(18	)	$	—
	Statutory surplus	189,698			220,004			—
	Contingency reserve	2,314			—			—
	NMIC's principal regulator is the Wisconsin OCI. Under applicable Wisconsin law, as well as that of 15 other states, a mortgage guaranty insurer must maintain a minimum amount of statutory capital relative to the risk-in-force (Risk to Capital ratio or “RTC ratio”) in order for the mortgage guaranty insurer to continue to write new business. We refer to these requirements as the “RTC requirement.” While formulations of minimum capital may vary in each jurisdiction that has such a requirement, the most common measure applied allows for a maximum permitted RTC ratio of 25 to 1. Wisconsin and certain other states, including California and Illinois, apply a substantially similar requirement referred to as minimum policyholders position. Our operation plan filed with the Wisconsin OCI and other state insurance departments in connection with NMIC's applications for licensure includes the expectation that NMIH will downstream additional capital if needed so that NMIC does not exceed an 18 to 1 risk-to-capital ratio. NMIC may in the future seek state insurance department approvals, as needed, of an amendment to our business plan to increase this ratio to the Wisconsin regulatory minimum of 25 to 1.
	Additionally, as a condition of GSE Approval, NMIC has agreed with Fannie Mae and Freddie Mac to limit NMIC's RTC ratio to no greater than 15 to 1 and to maintain total statutory capital of at least $150 million for a three year period ending on December 31, 2015. After that date, NMIC agreed to comply with the risk-to-capital ratios that are imposed in the GSEs' then existing eligibility requirements. As part of the state licensing process, NMIC entered into risk-to-capital agreements with the California Insurance Department, the Missouri Department of Insurance, the New York State Department of Financial Services, the Ohio Department of Insurance and the Texas Commissioner of Insurance. These agreements require NMIC to maintain a risk-to-capital ratio not to exceed 20 to 1 until January 15, 2016.
	Certain states limit the amount of risk a mortgage guaranty insurer may retain on a single loan to 25% of the indebtedness to the insured and as a result the portion of such insurance in excess of 25% must be reinsured. NMIC has entered into a primary excess share reinsurance agreement with Re One effective August 1, 2012. NMIC cedes premiums and claims to Re One on an excess share basis for any primary or pool policy which offers coverage greater than 25%. NMIC will use reinsurance provided by Re One solely for purposes of compliance with statutory coverage limits. During April 2013, NMIC wrote its first mortgage insurance policies and ceded premium and risk to Re One the following month.
	As of December 31, 2012, none of our insurance subsidiaries had written any business, had no risk-in-force and therefore had no ratios. As of December 31, 2013 NMIC's RTC ratio is less than 1:1, significantly below the limits established with the GSEs and state insurance departments.
	The risk-to-capital calculation for each of our insurance subsidiaries, as well as our combined risk-to-capital calculation, as of December 31, 2013, is presented below.
	As of December 31, 2013	NMIC			Re One			Combined
		(In Thousands)
	Pool risk-in-force (1)
	Direct	$	93,090		$	—		$	93,090
	Assumed	—			25,171			25,171
	Ceded	(25,171		)	—			(25,171		)
	Total pool risk-in-force	67,919			25,171			93,090
	Primary risk-in-force
	Direct	36,516			—			36,516
	Assumed	—			2,637			2,637
	Ceded	(2,637		)	—			(2,637		)
	Total primary risk-in-force	33,879			2,637			36,516
	Total risk-in-force	101,798			27,808			129,606
	Statutory policyholders' surplus	180,310			9,388			189,698
	Statutory contingency reserve	1,740			574			2,314
	Total statutory policyholders' position	182,050			9,962			192,012
	Risk-to-Capital (2)	0.6:1			2.8:1			0.7:1
	(1)	Pool risk-in-force as shown in the table above is equal to the aggregate stop loss less a deductible.
	(2)	Represents total risk-in-force divided by statutory policyholders' position which is the metric by which the majority of state insurance regulators will assess our capital adequacy. Additionally, Fannie Mae requires us to maintain the greater of (a) the risk-to-capital requirements outlined in the January 2013 approval letter, or (b) a risk-to-capital ratio of 18:1 on primary business plus statutory capital equal to the amount of net risk-in-force of the pool.
	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 (subject to certain limitations) recent net profits. As of December 31, 2012, NMIH's capital surplus was approximately $489 million. NMIH assets, which, excluding investment in NMIC and Re One, are approximately $276 million at December 31, 2013, are unencumbered by any debt or other subsidiary commitments or obligations. As such, at December 31, 2013, NMIH had sufficient resources to downstream to either insurance subsidiary the cash necessary to fully comply with all commitments. The insurance subsidiaries are both mono-line mortgage guaranty insurance companies and the assets of each are dedicated only to the support of direct risk and obligations of each mortgage insurance entity. NMIC only writes direct mortgage guaranty insurance business and assumes no business from any other entity. Re One only assumes business from NMIC to allow NMIC to comply with statutory risk requirements. Neither NMIC nor Re One have subsidiaries, and therefore do not have risks and obligations that compete for its resources, and neither entity counts a subsidiary's asset in their admitted statutory assets.
	The GSEs and state insurance regulators may restrict our insurance subsidiaries' ability to pay dividends to NMIH. See "Note 9, Commitments and Contingencies" for a discussion of the dividend restrictions imposed by the GSEs in the GSE Approval, as well as restrictions imposed by various states in conjunction with NMIC's receipt of certificates of authority in those states. In addition to the restrictions imposed during the GSE Approval and licensing process, the ability of our insurance subsidiaries to pay dividends to NMIH is limited by insurance laws of the State of Wisconsin and certain other states. Wisconsin law provides that an insurance company may pay out dividends without the prior approval of the Wisconsin OCI (“ordinary dividends”) in an amount, when added to other shareholder distributions made in the prior 12 months, not to exceed the lesser of (a) 10% of the insurer's surplus as regards to policyholders as of the prior December 31, or (b) its net income (excluding realized capital gains) for the twelve month period ending December 31 of the immediately preceding calendar year. In determining net income, an insurer may carry forward net income from the previous calendar years that has not already been paid out as a dividend. Dividends that exceed this amount are “extraordinary dividends”, which require prior approval of the Wisconsin OCI. As of December 31, 2013, the amount of restricted net assets held by our consolidated insurance subsidiaries totaled approximately $193 million of NMIH's consolidated net assets of $463 million. The amount of restricted assets used to determine any dividend to NMIH, once all restrictions expire, would be computed under SAP which may differ from the amount of restricted assets computed under GAAP.

Quarterly_Financial_Data_Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]	'
Quarterly Financial Data (Unaudited)	'
	Quarterly Financial Data (Unaudited)
		2013 Quarters												2013
		First			Second			Third			Fourth			Year
		(In Thousands, except share data)
	Net premiums written	$	—		$	1		$	482		$	3,058		$	3,541
	Net premiums earned	—			1			482			1,612			2,095
	Net investment income	410			1,407			1,519			1,472			4,808
	Net realized investment gains (losses)	28			452			(308		)	14			186
	Gain (Loss) from change in fair value of warrant liability	35			(1,115		)	469			(918		)	(1,529		)
	Insurance claims and claims expenses	—			—			—			—			—
	Amortization of deferred policy acquisition costs	—			—			—			1			1
	Other underwriting and operating expenses	12,426			17,019			16,035			15,263			60,743
	Net Loss	(11,953		)	(16,274		)	(13,873		)	(13,084		)	(55,184		)
	Loss per share (1)
	Basic and diluted loss per share	$	(0.22	)	$	(0.29	)	$	(0.25	)	$	(0.23	)	$	(0.99	)
	Weighted average common shares outstanding	55,500,100			55,629,932			55,637,480			57,238,730			56,005,326
		2012 Quarters												2012
		First			Second			Third			Fourth			Year
		(In Thousands, except share data)
	Net premiums written	$	—		$	—		$	—		$	—		$	—
	Net premiums earned	—			—			—			—			—
	Net investment income	—			—			1			5			6
	Net realized investment gains (losses)	—			—			—			—			—
	Gain (Loss) from change in fair value of warrant liability	—			—			—			278			278
	Insurance claims and claims expenses	—			—			—			—			—
	Amortization of deferred policy acquisition costs	—			—			—			—			—
	Other underwriting and operating expenses	386			6,196			8,114			13,079			27,775
	Net Loss	(386		)	(6,196		)	(8,113		)	(12,796		)	(27,491		)
	Loss per share (1)
	Basic and diluted loss per share	$	(3,860.00	)	$	(0.15	)	$	(0.15	)	$	(0.23	)	$	(0.73	)
	Weighted average common shares outstanding	100			40,252,847			55,500,100			55,500,100			37,909,936
	-1	Due to the use of weighted average shares outstanding when calculating earnings per share, the sum of quarterly per share data may not equal the per share data for the year.

SCHEDULE_I_SUMMARY_OF_INVESTME

SCHEDULE I - SUMMARY OF INVESTMENTS	12 Months Ended
	Dec. 31, 2013
Summary of Investments, Other than Investments in Related Parties [Abstract]	'
Summary of Investments, Other than Investments in Related Parties	'
	31-Dec-13	Amortized Cost		Fair Value		Amount Reflected on Balance Sheet
		(In Thousands)
	Fixed Maturities:
	Bonds:
	U.S. Treasury securities and obligations of U.S. government agencies	$	58,251	$	57,421	$	57,421
	Municipal bonds	5,259		5,204		5,204
	Corporate debt securities	130,499		127,928		127,928
	Asset-backed securities	39,014		38,511		38,511
	Total investments other than investments in related parties	$	233,023	$	229,064	$	229,064

SCHEDULE_II_FINANCIAL_INFORMAT

SCHEDULE II - FINANCIAL INFORMATION OF REGISTRANT	12 Months Ended
	Dec. 31, 2013
Condensed Financial Information of Parent Company Only Disclosure [Abstract]	'
Financial Information of Registrant Balance Sheets Parent Company Only	'
		31-Dec-13			31-Dec-12
		(In Thousands, except for share data)
	Assets
	Investments, available-for-sale	$	229,064		$	—
	Cash and cash equivalents	36,433			270,717
	Restricted cash	—			40,338
	Investment in subsidiaries, at equity in net assets	193,242			228,612
	Accrued investment income	1,038			—
	Prepaid expenses	1,519			417
	Due from affiliates, net	10,565			—
	Software and equipment, net	7,574			2,444
	Other assets	61			107
	Total Assets	$	479,496		$	542,635
	Liabilities
	Accounts payable and accrued expenses	$	9,908		$	8,707
	Placement fee payable	—			38,305
	Purchase consideration payable	—			2,033
	Warrant liability, at fair value	6,371			4,842
	Total Liabilities	16,279			53,887
	Shareholders' Equity
	Common stock - Class A shares, $0.01 par value,	581			553
	58,052,480 and 55,250,100 shares issued and outstanding as of December 31, 2013 and December 31, 2012, respectively (250,000,000 shares authorized)
	Common stock - Class B shares, $0.01 par value, 0 and 250,000 shares issued and outstanding as of December 31, 2013 and December 31, 2012, respectively (250,000 authorized)	—			2
	Additional paid-in capital	553,707			517,032
	Accumulated other comprehensive (loss) income	(7,047		)	1
	Accumulated deficit	(84,024		)	(28,840		)
	Total Shareholders' Equity	463,217			488,748
	Total Liabilities and Shareholders' Equity	$	479,496		$	542,635
		For the Year Ended December 31,						For the Period from May 19, 2011 (inception) to December 31, 2011
		2013			2012
		(In Thousands)
	Revenues
	Net investment income	$	2,758		$	2		$	—
	Net realized investment gains	188			—			—
	(Loss) Gain from change in fair value of warrant liability	(1,529		)	278			—
	Total Revenues	1,417			280			—
	Expenses
	Other operating expenses	24,319			26,575			1,349
	Total Expenses	24,319			26,575			1,349
	Equity in net loss of subsidiaries	(32,282		)	(1,196		)	—
	Net Loss	$	(55,184	)	$	(27,491	)	$	(1,349	)
		For the Year Ended December 31, 2013			For the Year Ended December 31, 2012			For the Period May 19, 2011 (inception) to December 31, 2011
	Cash Flows from Operating Activities	(In Thousands)
	Net loss	$	(55,184	)	$	(27,491	)	$	(1,349	)
	Adjustments to reconcile net loss to net cash used in operating activities:
	Share-based compensation expense	10,367			6,115			—
	Warrants issued in connection with line of credit	—			1,620			—
	Loss (gain) from change in fair value of warrant liability	1,529			(278		)	—
	Net realized investment gains	(188		)	—			—
	Depreciation and other amortization	3,325			3			—
	Accrued investment income	(1,038		)	(2		)	—
	Changes in operating assets and liabilities:
	Receivable from affiliates	(10,565		)	—			—
	Prepaid expenses	(1,102		)	(234		)	(183		)
	Other assets	32,326			1,118			(26		)
	Accounts payable and accrued expenses	623			4,550			1,353
	Net Cash Used in Operating Activities	(19,907		)	(14,599		)	(205		)
	Cash Flows from Investing Activities
	Capitalization of subsidiaries	—			(220,000		)	—
	Purchase of fixed maturities, available-for-sale	(293,470		)	—			—
	Proceeds from sale of fixed maturities, available-for-sale	59,454			—			—
	Purchase of software and equipment	(6,695		)	(2,444		)	—
	Acquisition of subsidiaries	—			(2,500		)	—
Net Cash Used in Investing Activities	(240,711		)	(224,944		)	—
Cash Flows from Financing Activities
(Payments) Proceeds on line of credit	—			—			205
Payment of financing debt	—			(205		)	—
Issuance of common stock	27,912			510,465			—
Taxes paid related to net share settlement of equity awards	(1,578		)	—			—
Net Cash Provided by Financing Activities	26,334			510,260			205
Net (Decrease) Increase in Cash and Cash Equivalents	(234,284		)	270,717			—
Cash and Cash Equivalents, beginning of period	270,717			—			—
Cash and Cash Equivalents, end of period	$	36,433		$	270,717		$	—
Note A
The NMI Holdings, Inc. (the “Parent Company”) financial statements represent the stand-alone financial statements of the Parent Company. These financial statements have been prepared on the same basis and using the same accounting policies as described in the consolidated financial statements included herein. Refer to the Parent Company’s consolidated financial statements for additional information.
Revisions to Prior Periods
Certain other prior balances have been reclassified to conform to the current period presentation.
Note B
Our insurance subsidiaries are subject to statutory regulations as to maintenance of policyholders' surplus and payment of dividends. The maximum amount of dividends that the insurance subsidiaries may pay in any twelve-month period without regulatory approval by the Office of the Commissioner of Insurance of the State of Wisconsin is the lesser of adjusted statutory net income or 10% of statutory policyholders' surplus as of the preceding calendar year end. Adjusted statutory net income is defined for this purpose to be the greater of statutory net income, net of realized investment gains, for the calendar year preceding the date of the dividend or statutory net income, net of realized investment gains, for the three calendar years preceding the date of the dividend less dividends paid within the first two of the preceding three calendar years.
Note C
The Parent Company provides certain services to its subsidiaries. The Parent Company allocates to its subsidiaries corporate expense it incurs in the capacity of supporting those subsidiaries, based on either an allocated percentage of time spent or internally allocated capital. Total operating expenses allocated to subsidiaries for 2013 were $32.5 million. No expenses were allocated to subsidiaries during 2012 or 2011. Amounts charged to the subsidiaries for operating expenses are based on actual cost, without any mark-up. The Parent Company considers these charges fair and reasonable. The subsidiaries reimburse the Parent Company for these costs in a timely manner, which has the impact of improving the cash flows of the Parent Company.

SCHEDULE_IV_FINANCIAL_INFORMAT

SCHEDULE IV - FINANCIAL INFORMATION OF REGISTRANT REINSURANCE	12 Months Ended
	Dec. 31, 2013
Supplemental Schedule of Reinsurance Premiums for Insurance Companies [Abstract]	'
Financial Information of Registrant Reinsurance Parent Company Only	'
	The Parent Company has no reinsurance agreements. The insurance subsidiaries are both mono-line mortgage guaranty insurance companies and the assets of each are dedicated only to the support of our mortgage insurance operations. NMIC only writes direct mortgage guaranty insurance business and assumes no business from any other entity. Re One only assumes business from NMIC to allow NMIC to comply with statutory risk requirements. Neither NMIC nor Re One count any subsidiary of any kind in their admitted statutory assets.

Summary_of_Accounting_Policies1

Summary of Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Cash and Cash Equivalents	'
	Cash and Cash Equivalents
	We consider items such as certificates of deposit and money market funds with original maturities of 90 days or less to be cash equivalents.
	There was no restricted cash as of December 31, 2013; however, we had restricted cash as of December 31, 2012. The restricted cash balance was comprised of two escrow accounts that were initially funded on April 24, 2012, in connection with our Private Placement, with an agreement that the funds would be released to FBR and MAC Financial Ltd. upon GSE Approval. On January 23, 2013, after receipt of GSE approval, the restricted cash was released from escrow.
Investments	'
	Investments
	We have designated our investment portfolio as available-for-sale and report it at fair value. The related unrealized gains and losses are, after considering the related tax expense or benefit, recognized as a component of accumulated other comprehensive (loss) income in shareholders' equity. Net realized investment gains and losses are reported in income based upon specific identification of securities sold.
	Purchases and sales of investments are recorded on a trade date basis. Net investment income is recognized when earned and includes interest and dividend income together with amortization of market premiums and discounts using the effective yield method and is net of investment management fees and other investment related expenses. For asset-backed securities and any other holdings for which there is a prepayment risk, prepayment assumptions are evaluated and revised as necessary. Any adjustments required due to the change in effective yields and maturities are recognized on a prospective basis through yield adjustments.
	Each quarter we evaluate our investments in order to determine whether declines in fair value below amortized cost were considered other-than-temporary in accordance with applicable guidance. In evaluating whether a decline in fair value is other-than-temporary, we consider several factors including, but not limited to:
	•	our intent to sell the security or whether it is more likely than not that we will be required to sell the security before recovery;
	•	severity and duration of the decline in fair value;
	•	the financial condition of the issuer;
	•	the failure of the issuer to make scheduled interest or principal payments;
	•	recent credit downgrades of the applicable security or the issuer below investment grade; and
	•	adverse conditions specifically related to the security, an industry, or a geographic area.
	Under the current guidance, a debt security impairment is deemed other than temporary if (i) we either intend to sell the security, or it is more likely than not that we will be required to sell the security before recovery or (ii) we do not expect to collect cash flows sufficient to recover the amortized cost basis of the security. In the event of the decline in fair value of a debt security, a holder of that security that does not intend to sell the debt security and for whom it is more likely than not that such holder will be required to sell the debt security before recovery of its amortized cost basis is required to separate the decline in fair value into (a) the amount representing the credit loss and (b) the amount related to other factors. The amount of total decline in fair value related to the credit loss shall be recognized in earnings as OTTI with the amount related to other factors recognized in accumulated other comprehensive income or loss, net of tax. In periods after recognition of an OTTI on debt securities, we account for such securities as if they had been purchased on the measurement date of the OTTI at an amortized cost basis equal to the previous amortized cost basis less the OTTI recognized in earnings. For debt securities for which OTTI were recognized in earnings, the difference between the new amortized cost basis and the cash flows expected to be collected will be accreted into net investment income. The determination of OTTI is a subjective process, and different judgments and assumptions could affect the timing of the loss realization.
Revenue Recognition	'
	Revenue Recognition
	In the mortgage guaranty insurance industry, a “book” is a group of loans that an MI company insures in a particular period, normally a calendar year. We set premiums at the time a policy is issued based on our expectations regarding likely performance over the term of coverage. The policies we write are guaranteed renewable contracts at the policyholder's option on a single, annual or monthly premium basis. We generally have no ability to re-underwrite or reprice these contracts. However, we review every loan and through this review process confirm underwriting eligibility, either prior to loan closing in the non-delegated channel or through a post-closing underwriting review in the delegated channel. Based on this review, we may re-price. Premiums written on a single premium basis and an annual premium basis are initially deferred as unearned premium reserve and earned over the policy term.  Premiums written on policies covering more than one year are amortized over the policy life in accordance with the expiration of risk which is the anticipated claim payment pattern based on industry experience.  Premiums written on annual policies are earned on a monthly pro rata basis.  Premiums written on monthly policies are earned as coverage is provided. Premiums written on pool transactions are earned over the period that coverage is provided.  Upon cancellation of a policy, all premium that is non-refundable is immediately earned. Any refundable premium is returned to the policyholder. Premiums returned to policyholders are recorded as a reduction of written and earned premiums in the current period. The actual return of premium for all periods affects premiums written and earned in those periods.
Deferred Policy Acquisition Costs	'
	Deferred Policy Acquisition Costs
	Costs directly associated with the successful acquisition of mortgage guaranty 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"). For each book year of business, these costs are amortized to income in proportion to estimated gross profits over the estimated life of the policies.
Business Combinations, Goodwill and Intangible Assets	'
	Business Combinations, Goodwill and Intangible Assets
	Goodwill represents the excess of the purchase price over the estimated fair value of net assets acquired from a business combination. In accordance with ASC 350, Intangibles - Goodwill and Other, we test goodwill for impairment during the third quarter each year or more frequently if we believe indicators of impairment exist. We have not identified any impairments of goodwill through December 31, 2013.
	Our intangible assets consist of state licenses and GSE applications which have indefinite lives. We test indefinite-lived intangible assets for impairment during the fourth quarter of each year or more frequently if we believe indicators of impairment exist. We do not believe that the indefinite-lived intangible assets were impaired as of December 31, 2013.
Software and Equipment	'
	Software and Equipment
	Software and equipment are stated at cost, less accumulated amortization and depreciation. Amortization and depreciation are calculated using the straight-line method over the estimated useful lives of the respective assets ranging typically from 3 to 7 years, unless factors indicate a shorter useful life. Amortization of software and depreciation of equipment commences at the beginning of the month following the placement of the assets into use by us. We have reduced the useful life of our insurance management system. For further detail see "Note 7, Software and Equipment.
Warrants	'
	Warrants
	We account for warrants to purchase our common shares in accordance with ASC 470-20 Debt with Conversion and Other Options and ASC 815-40 Derivatives and Hedging - Contracts in Entity's Own Equity. Our outstanding warrants, issued to FBR and former stockholders of MAC Financial Ltd., may be settled by us using either (i) physical settlement method or (ii) cashless exercise, where shares that are issued upon exercise of the warrants are reduced, to cover the cost of the exercise, in lieu of the holder remitting a cash payment of the exercise price. The warrants expire and are not exercisable on the 10th anniversary after the date the warrant was issued. The exercise price and the number of warrants are subject to anti-dilution provisions whereby the existing exercise price is adjusted downward, and the number of warrants increased, for events that may not be dilutive. The adjustment may be in excess of any dilution suffered. As a result, the warrants are classified as a liability. We revalue the warrants at the end of each reporting period and any change in fair value is reported in the statements of operations in the period in which the change occurred. The fair value of the warrants is calculated using a Black-Scholes option-pricing model in combination with a binomial model and a Monte Carlo simulation model used to value the pricing protection features within the warrant.
Share-based Compensation	'
	Share-Based Compensation
	We account for stock compensation in accordance with ASC 718, Compensation - Stock Compensation. This addresses accounting for share-based awards and recognition of compensation expense, measured using grant date fair value, over the requisite service or performance period of the award. Share-based payments include RSUs and stock option grants under the 2012 Stock Incentive Plan. The fair value of stock option grants issued are determined based on an option pricing model which takes into account various assumptions that are subjective. Key assumptions used in the stock option valuation include the expected term of the equity award taking into account the contractual term of the award, the effects of expected exercise and post-vesting termination behavior, expected volatility, expected dividends and the risk-free interest rate for the expected term of the award. RSU grants to employees contain a market condition and/or service condition. The fair value of RSU grants to employees with a market condition is determined based on a Monte Carlo simulation model at the date of grant. RSU grants to employees with a service condition and RSU grants to non-employee directors are valued at our stock price on the date of grant less the present value of anticipated dividends.
Offering and Incorporation Expenses	'
	Offering and Incorporation Expenses
	Offering expenses incurred in connection with our capitalization were recorded as a reduction of paid-in-capital at closing. These costs include certain investment banking fees, legal fees, printer fees and audit fees. Any incorporation and organizational expenses not related to the raising of capital are expensed as incurred and are included in the statement of operations.
Reserve for Insurance Claims and Claims Expenses	'
	Reserve for Insurance Claims and Claims Expenses
	We establish 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 claims reserves only for loans in default. We are a new company and have only recently commenced transacting mortgage guaranty insurance. We have not received any primary NODs, and thus have not established any primary reserves for claims or IBNR for the years ended December 31, 2013, 2012 or 2011. Additionally, we entered into a pool insurance transaction with Fannie Mae, effective September 1, 2013. For this pool transaction, any claims reserve potentially established would be in excess of the transaction's deductible, which represents the amount payable by Fannie Mae on initial claims. The consideration of the deductible would serve to delay the recording of any claim reserve until estimated claims exceed the deductible amount. In addition, all of the loans in the pool have LTVs below 80%. As a result, the potential for any one default to result in a loss to the insured is mitigated. We have not established any pool reserves for claims or IBNR for the years ended December 31, 2013, 2012 or 2011. See "Note 9, Commitments and Contingencies", for more information on this pool transaction.
Premium Deficiency Reserves	'
	Premium Deficiency Reserves
	After our insurance claim reserves are established, we will perform a premium deficiency calculation 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. Because we have not established any reserves, as discussed above, we have also determined that no premium deficiency reserves were necessary for the years ended December 31, 2013, 2012 or 2011.
Income Taxes	'
	Income Taxes
	We account for income taxes using the liability method in accordance with ASC 740 - Income Taxes. The liability method measures the expected future tax effects of temporary differences at the enacted tax rates applicable for the period in which the deferred asset or liability is expected to be realized or settled. Temporary differences are differences between the tax basis of an asset or liability and its reported amount in the consolidated financial statements that will result in future increases or decreases in taxes owed on a cash basis compared to amounts already recognized as tax expense in the consolidated statement of operations.
	We evaluate the need for a valuation allowance against our deferred tax assets on a quarterly basis. In the course of our review, we assess all available evidence, both positive and negative, including future sources of income, tax planning strategies, future contractual cash flows and reversing temporary differences. Additional valuation allowance benefits or charges could be recognized in the future due to changes in our expectation regarding the realization of tax benefits. Uncertain tax positions taken or expected to be taken in a tax return by us are recognized in the financial statements when it is more likely than not that the position would be sustained upon examination by tax authorities. There are no tax uncertainties that are expected to result in significant increases or decreases to unrecognized tax benefits within the next twelve month period.
	In assessing the valuation of deferred tax assets, we consider whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible.
Clarifying the Scope of Disclosures about Offsetting Assets and Liabilities	'
	Clarifying the Scope of Disclosures about Offsetting Assets and Liabilities
	In January 2013, the FASB issued an Accounting Standards Update clarifying that the scope of Update 2011-11, Balance Sheet (Topic 210): Disclosures about Offsetting Assets and Liabilities, applies to derivatives accounted for in accordance with Topic 815, Derivatives and Hedging, including bifurcated embedded derivatives, repurchase agreements and reverse repurchase agreements, and securities borrowing and securities lending transactions that are either offset in accordance with Section 210-20-45 or Section 815-10-45 or subject to an enforceable master netting arrangement or similar agreement. The amendments are effective for fiscal years beginning on or after January 1, 2013, and interim periods within those annual periods. The adoption of this guidance in January 2013 did not have any effect on our results of operations, financial position or liquidity.
Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income	'
	Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income
	In February 2013, the FASB issued an Accounting Standards Update addressing the reporting of reclassifications out of accumulated other comprehensive income. The Update requires an entity to report the effect of significant reclassifications out of accumulated other comprehensive income on the respective line items in the statement of operations if the amount being reclassified is required under GAAP to be reclassified in its entirety to net income. For other amounts that are not required under GAAP to be reclassified in their entirety to net income in the same reporting period, an entity is required to cross-reference other disclosures required under GAAP that provide additional detail about those amounts. The adoption of this guidance in December 2013 did not have any impact on our results of operations, financial position or liquidity.
Reclassifications	'
	Reclassifications
	Certain items in the financial statements as of December 31, 2012 and for the periods ending December 31, 2012 and December 31, 2011 have been reclassified to conform to the current period's presentation. There was no effect on net income or shareholders' equity previously reported.

Acquisition_of_MAC_Tables

Acquisition of MAC (Tables)	12 Months Ended
	Dec. 31, 2013
Business Combinations [Abstract]	'
Schedule of Assets Acquired and Liabilities Assumed	'
	The consideration (net of expenses paid on MAC's behalf) was held in an escrow account until we received GSE Approval, upon which time it was released to MAC Financial Ltd. The total purchase consideration was allocated to the acquired assets and liabilities as follows:
	April 24, 2012	(In Thousands)
	Current assets	$	52
	Intangibles	1,590
	Capitalized software	5,000
	Goodwill	3,244
	Subtotal	9,886
	Current liabilities and deferred tax liabilities	(1,386		)
	Estimated fair value of net assets acquired	$	8,500

Investments_Tables

Investments (Tables)	12 Months Ended
	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]	'
Schedule of Fair Values and Gross Unrealized Gains and Losses	'
	Fair Values and Gross Unrealized Gains and Losses on Investments
		Amortized				Gross Unrealized							Fair
		Cost				Gains			(Losses)				Value
	As of December 31, 2013	(In Thousands)
	U.S. Treasury securities and obligations of U.S. government agencies	$	108,067			$	—		$	(1,461	)		$	106,606
	Municipal bonds	12,017				1			(85		)		11,933
	Corporate debt securities	221,899				157			(4,799		)		217,257
	Asset-backed securities	74,152				114			(974		)		73,292
	Total bonds	416,135				272			(7,319		)		409,088
	Short-term investments	39,695				—			—				39,695
	Total Investments	$	455,830			$	272		$	(7,319	)		$	448,783
		Amortized				Gross Unrealized							Fair
		Cost				Gains			(Losses)				Value
	As of December 31, 2012	(In Thousands)
	Short-term investments	$	4,863			$	1		$	—			$	4,864
	Total Investments	$	4,863			$	1		$	—			$	4,864
Schedule of Investments by Maturity	'
	The amortized cost and fair values of available for sale securities at December 31, 2013, 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.
		Amortized				Fair
		Cost				Value
		(In Thousands)
	Due in one year or less	$	—			$	—
	Due after one through five years	260,855				257,501
	Due after five through ten years	65,687				63,440
	Due after ten years	15,441				14,855
	Asset-backed securities	74,152				73,292
	Total Bonds	$	416,135			$	409,088
Schedule of Realized Investment (Losses) Gains on Investments	'
	Net Realized Investment Gains (Losses) on Investments
		For the Year Ended December 31, 2013
		(In Thousands)
	Corporate Bond	$	323
	U.S. Treasury securities and obligations of U.S. government agencies	(87		)
	Mortgage-backed security	(50		)
	Total Net Realized Investment Gains	$	186
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
		Fair Value			Unrealized Losses			Fair Value			Unrealized Losses				Fair Value		Unrealized Losses
	As of December 31, 2013	(In Thousands)
	U.S. Treasury securities and obligations of U.S. government agencies	$	106,606		$	(1,461	)	$	—		$	—			$	106,606	$	(1,461	)
	Municipal bonds	4,915			(85		)	—			—				4,915		(85		)
	Corporate debt securities	187,714			(4,799		)	—			—				187,714		(4,799		)
	Assets-backed securities	58,225			(974		)	—			—				58,225		(974		)
	Total Bonds	$	357,460		$	(7,319	)	$	—		$	—			$	357,460	$	(7,319	)
Schedule of Net Investment Income	'
	Net investment income is comprised of the following:
		For the Year Ended December 31, 2013				For the Year Ended December 31, 2012			For the Period May 19, 2011 (inception) to December 31, 2011
		(In Thousands)
	Fixed maturities	$	5,289			$	4		$	—
	Cash equivalents	—				2			—
	Other	2				—			—
	Investment income	5,291				6			—
	Investment expenses	(483		)		—			—
	Net Investment Income	$	4,808			$	6		$	—

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2013
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 as of December 31, 2013 and December 31, 2012:
		Fair Value Measurements Using
	Assets and Liabilities at Fair Value	Quoted Prices in		Significant Other		Significant		Fair Value
		Active Markets for		Observable Inputs		Unobservable
		Identical Assets		(Level 2)		Inputs
		(Level 1)				(Level 3)
	As of December 31, 2013	(In Thousands)
	U.S. Treasury securities and obligations of U.S. government agencies	$	49,484	$	57,122	$	—	$	106,606
	Municipal bonds	—		11,933		—		11,933
	Corporate debt securities	—		217,257		—		217,257
	Asset-backed securities	—		73,292		—		73,292
	Cash and cash equivalents	55,929		—		—		55,929
	Total Assets	$	105,413	$	359,604	$	—	$	465,017
	Warrant liability	—		—		$	6,371	$	6,371
	Total Liabilities	$	—	$	—	$	6,371	$	6,371
		Fair Value Measurements Using
	Assets and Liabilities at Fair Value	Quoted Prices in		Significant Other		Significant		Fair Value
		Active Markets for		Observable Inputs		Unobservable
		Identical Assets		(Level 2)		Inputs
		(Level 1)				(Level 3)
	As of December 31, 2012	(In Thousands)
	U.S. Treasury securities and obligations of U.S. government agencies	$	4,864	$	—	$	—	$	4,864
	Cash and cash equivalents	526,194		—		—		526,194
	Total Assets	$	531,058	$	—	$	—	$	531,058
	Warrant liability	—		—		$	4,842	$	4,842
	Total Liabilities	$	—	$	—	$	4,842	$	4,842
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation	'
	The following is a roll-forward of Level 3 liabilities measured at fair value for the year ended December 31, 2013:
		Warrant Liability
	Year Ended December 31, 2013	(In Thousands)
	Level 3 Instruments Only
	Balance, January 1, 2013	$	4,842
	Change in fair value of warrant liability included in earnings	1,529
	Balance, December 31, 2013	$	6,371

Software_and_Equipment_Tables

Software and Equipment (Tables)	12 Months Ended
	Dec. 31, 2013
Property, Plant and Equipment [Abstract]	'
Schedule of Equipment and Software	'
	Software and equipment, net of accumulated amortization and depreciation, as of December 31, consist of the following:
		2013			2012
		(In Thousands)
	Software	$	14,140		$	7,268
	Equipment	542			285
	Leasehold improvements	141			—
	Less accumulated amortization and depreciation	(5,947		)	(3		)
	Software and equipment, net	$	8,876		$	7,550

Intangible_Assets_and_Goodwill1

Intangible Assets and Goodwill (Tables)	12 Months Ended
	Dec. 31, 2013
Goodwill and Intangible Assets Disclosure [Abstract]	'
Schedule of Indefinite-Lived Intangible Assets	'
	Intangible assets and goodwill, net, as of December 31, 2013 and December 31, 2012, consist of the following:
	As of December 31, 2013 and December 31, 2012	(In Thousands)		Expected Lives
	Goodwill	$	3,244	Indefinite
	State licenses	260		Indefinite
	GSE approvals	130		Indefinite
	Total Intangible Assets and Goodwill	$	3,634

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Schedule of Future Minimum Lease Payments	'
	Management expects that, in the normal course of business, as of December 31, 2013, future minimum lease payments under this lease will be as follows:
	Years ending December 31,	(In Thousands)
	2014	$	1,570
	2015	1,670
	2016	1,741
	2017	1,489
	Totals	$	6,470

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2013
Income Tax Disclosure [Abstract]	'
Schedule of Deferred Tax Assets and Liabilities	'
	Following is a reconciliation of our net deferred income tax asset as of December 31, 2013 and December 31, 2012:
		December 31, 2013
		Gross				Tax Effected
	Deferred tax asset:	(In Thousands)
	Capitalized start-up costs	$	2,579			$	903
	Stock compensation	14,701				5,990
	Unrealized loss on investments	7,047				2,694
	Net operating loss carry forwards	65,276				24,602
	Other	10,118				3,760
	Total gross deferred tax assets	99,721				37,949
	Less: valuation allowance	(94,497		)		(35,778		)
	Total deferred tax assets	5,224				2,171
	Deferred tax liability:
	Capitalized software	(5,008		)		(2,095		)
	Intangible assets	(390		)		(133		)
	Other	(216		)		(76		)
	Total deferred tax liabilities	(5,614		)		(2,304		)
	Net deferred income tax liability	$	(390	)		$	(133	)
		December 31, 2012
		Gross				Tax Effected
	Deferred tax asset:	(In Thousands)
	Capitalized start-up costs	$	21,796			$	7,411
	Net operating loss carry forwards	7,307				2,484
	Total gross deferred tax assets	29,103				9,895
	Less: valuation allowance	(24,103		)		(8,195		)
	Total deferred tax assets	5,000				1,700
	Deferred tax liability:
	Capitalized software	(5,000		)		(1,700		)
	Intangible assets	(390		)		(133		)
	Total deferred tax liabilities	(5,390		)		(1,833		)
	Net deferred income tax liability	$	(390	)		$	(133	)
Schedule of Effective Income Tax Rate Reconciliation	'
	Reconciliation of the federal statutory income tax (benefit) rate to the effective income tax (benefit) rate is as follows:
		Year Ended December 31, 2013			For the Year Ended December 31, 2012
	Federal statutory income tax rate	35	%		35	%
	Loss on impairment	—			(1.48	)
	Prior year adjustment	3.52			1.66
	Other	1.66			(1.00	)
	Valuation allowance	(40.18	)		(28.00	)
	Purchase accounting adjustment	—			(6.18	)
	Effective income tax rate	—	%		—	%

ShareBased_Compensation_Tables

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Schedule of Stock Option Activity	'
	A summary of option activity in the plan during the years ending December 31, 2013 and December 31, 2012 is as follows:
	Option Activity	Shares		Weighted Average Exercise Price		Weighted Average Grant Date Fair Value per Share
		(Shares in Thousands)
	Options balance outstanding at December 31, 2012	2,547		$	10	$	3.86
	Options granted	532		11.78		4.57
	Less: Options forfeited	(15	)	10		3.84
	Less: Options canceled	(1	)	10		3.84
	Options balance outstanding at December 31, 2013	3,063		$	10.31	$	3.98
	Option Activity	Shares		Weighted Average Exercise Price		Weighted Average Grant Date Fair Value per Share
		(Shares in Thousands)
	Options balance outstanding at December 31, 2011	—		$	—	$	—
	Options granted	2,829		10		3.87
	Less: Options forfeited	(282	)	10		3.88
	Less: Options canceled	—		—		—
	Options balance outstanding at December 31, 2012	2,547		$	10	$	3.86
Schedule of Grant Date Fair Values of Stock Options, Valuation Assumptions	'
	The estimated grant date fair values of the stock options granted during 2013 and 2012 were calculated using the Black-Scholes valuation model based on the following assumptions:
		2013		2012
	Expected life	6 years		6 years
	Risk free interest rate	0.98% - 1.12%		0.85% - 1.12%
	Dividend yield	0	%	0	%
	Expected stock price volatility	39	%	39	%
	Projected forfeiture rate	1	%	1	%
Schedule of Restricted Stock Units Activity	'
	A summary of RSU activity in the plan during the years ending December 31, 2013 and December 31, 2012 is as follows:
		Shares		Weighted Average Grant Date Fair Value per Share
		(Shares in Thousands)
	Non-vested restricted stock units at December 31, 2012	1,429		$	7.35
	Restricted stock units granted	76		12.03
	Less: Restricted stock units vested	(263	)	6.79
	Less: Restricted stock units forfeited	—		—
	Non-vested restricted stock units at December 31, 2013	1,242		$	7.75
		Shares		Weighted Average Grant Date Fair Value per Share
		(Shares in Thousands)
	Non-vested restricted stock units at December 31, 2011	—		$	—
	Restricted stock units granted	1,667		7.35
	Less: Restricted stock units forfeited	(238	)	7.35
	Non-vested restricted stock units at December 31, 2012	1,429		$	7.35
Schedule of Grant Date Fair Value of Restricted Stock Units, Valuation Assumptions	'
	The estimated grant date fair values of the RSUs granted in 2012 that are subject to both a market and service condition were calculated using a Monte Carlo simulation model based on the average outcome of 150,000 simulations using the following assumption:
	Expected life	5 years
	Risk free interest rate	0.86	%
	Dividend yield	0	%
	Expected stock price volatility	39	%
	Projected forfeiture rate	1	%

Statutory_Information_Tables

Statutory Information (Tables)	12 Months Ended
	Dec. 31, 2013
Insurance [Abstract]	'
Schedule of Risk to Capital	'
	The risk-to-capital calculation for each of our insurance subsidiaries, as well as our combined risk-to-capital calculation, as of December 31, 2013, is presented below.
	As of December 31, 2013	NMIC			Re One			Combined
		(In Thousands)
	Pool risk-in-force (1)
	Direct	$	93,090		$	—		$	93,090
	Assumed	—			25,171			25,171
	Ceded	(25,171		)	—			(25,171		)
	Total pool risk-in-force	67,919			25,171			93,090
	Primary risk-in-force
	Direct	36,516			—			36,516
	Assumed	—			2,637			2,637
	Ceded	(2,637		)	—			(2,637		)
	Total primary risk-in-force	33,879			2,637			36,516
	Total risk-in-force	101,798			27,808			129,606
	Statutory policyholders' surplus	180,310			9,388			189,698
	Statutory contingency reserve	1,740			574			2,314
	Total statutory policyholders' position	182,050			9,962			192,012
	Risk-to-Capital (2)	0.6:1			2.8:1			0.7:1
	(1)	Pool risk-in-force as shown in the table above is equal to the aggregate stop loss less a deductible.
	(2)	Represents total risk-in-force divided by statutory policyholders' position which is the metric by which the majority of state insurance regulators will assess our capital adequacy. Additionally, Fannie Mae requires us to maintain the greater of (a) the risk-to-capital requirements outlined in the January 2013 approval letter, or (b) a risk-to-capital ratio of 18:1 on primary business plus statutory capital equal to the amount of net risk-in-force of the pool.
	NMIC and Re One's combined statutory net income, statutory surplus and contingency reserve as of and for the years ended December 31, 2012 , 2011 and 2010 were as follows:
		December 31,
		2013			2012			2011
		(In Thousands)
	Statutory net loss	$	(33,307	)	$	(18	)	$	—
	Statutory surplus	189,698			220,004			—
	Contingency reserve	2,314			—			—

Quarterly_Financial_Data_Unaud1

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]	'
Schedule of Quarterly Financial Information	'
		2013 Quarters												2013
		First			Second			Third			Fourth			Year
		(In Thousands, except share data)
	Net premiums written	$	—		$	1		$	482		$	3,058		$	3,541
	Net premiums earned	—			1			482			1,612			2,095
	Net investment income	410			1,407			1,519			1,472			4,808
	Net realized investment gains (losses)	28			452			(308		)	14			186
	Gain (Loss) from change in fair value of warrant liability	35			(1,115		)	469			(918		)	(1,529		)
	Insurance claims and claims expenses	—			—			—			—			—
	Amortization of deferred policy acquisition costs	—			—			—			1			1
	Other underwriting and operating expenses	12,426			17,019			16,035			15,263			60,743
	Net Loss	(11,953		)	(16,274		)	(13,873		)	(13,084		)	(55,184		)
	Loss per share (1)
	Basic and diluted loss per share	$	(0.22	)	$	(0.29	)	$	(0.25	)	$	(0.23	)	$	(0.99	)
	Weighted average common shares outstanding	55,500,100			55,629,932			55,637,480			57,238,730			56,005,326
		2012 Quarters												2012
		First			Second			Third			Fourth			Year
		(In Thousands, except share data)
	Net premiums written	$	—		$	—		$	—		$	—		$	—
	Net premiums earned	—			—			—			—			—
	Net investment income	—			—			1			5			6
	Net realized investment gains (losses)	—			—			—			—			—
	Gain (Loss) from change in fair value of warrant liability	—			—			—			278			278
	Insurance claims and claims expenses	—			—			—			—			—
	Amortization of deferred policy acquisition costs	—			—			—			—			—
	Other underwriting and operating expenses	386			6,196			8,114			13,079			27,775
	Net Loss	(386		)	(6,196		)	(8,113		)	(12,796		)	(27,491		)
	Loss per share (1)
	Basic and diluted loss per share	$	(3,860.00	)	$	(0.15	)	$	(0.15	)	$	(0.23	)	$	(0.73	)
	Weighted average common shares outstanding	100			40,252,847			55,500,100			55,500,100			37,909,936
	-1	Due to the use of weighted average shares outstanding when calculating earnings per share, the sum of quarterly per share data may not equal the per share data for the year.

Organization_and_Basis_of_Pres1

Organization and Basis of Presentation (Details) (USD $)	1 Months Ended	7 Months Ended	12 Months Ended		1 Months Ended		0 Months Ended		1 Months Ended
	Apr. 30, 2012	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Nov. 30, 2011	Apr. 30, 2012	Nov. 12, 2013	Nov. 08, 2013	Nov. 30, 2011
					MAC Financial Holding Corporation and Subsidiaries [Member]	Common Class A [Member]	IPO [Member]	IPO [Member]	IPO [Member]
Business Acquisition [Line Items]	'	'	'	'	'	'	'	'	'
Cash, common stock and warrants issued for acquisition	'	'	'	'	$8,500,000	'	'	'	'
Liabilities assumed in acquisition	'	'	'	'	1,300,000	'	'	'	'
Tax liabilities assumed in acquisition	'	'	'	'	100,000	'	'	'	'
Common stock offered and sold, (in shares)	'	'	'	'	'	55,000,000	'	2,100,000	2,400,000
Common stock issue price (usd per share)	'	'	'	'	'	$10	'	'	'
Issuance of common stock	'	0	27,912,000	510,465,000	'	550,000,000	'	'	'
Underwriting fee and other offering expense (percent)	7.00%	'	'	'	'	'	6.00%	'	'
Underwriting fee and other offering expense	$510,000,000	'	'	'	'	'	$28,000,000	'	'
Antidilutive securities excluded from computation of earnings per share (in shares)	'	'	5,303,394	4,414,165	'	'	'	'	'

Summary_of_Accounting_Policies2

Summary of Accounting Policies (Details)	Dec. 31, 2013	Apr. 24, 2012	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013
	insured	escrow_account	Minimum [Member]	Minimum [Member]	Maximum [Member]	Maximum [Member]	Customer Concentration Risk [Member]	Geographic Concentration Risk [Member]
			Software [Member]	Equipment [Member]	Software [Member]	Equipment [Member]	Sales Revenue, Net [Member]	Sales Revenue, Net [Member]
Finite-Lived Intangible Assets [Line Items]	'	'	'	'	'	'	'	'
Number of escrow accounts, funds released upon GSE approval	'	2	'	'	'	'	'	'
Number of customers	1	'	'	'	'	'	'	'
Concentration risk	'	'	'	'	'	'	97.00%	28.00%
Estimated useful life	'	'	'3 years	'3 years	'7 years	'7 years	'	'

Common_Stock_Offering_Details

Common Stock Offering (Details) (USD $)	1 Months Ended	12 Months Ended		1 Months Ended	12 Months Ended	0 Months Ended		1 Months Ended
In Millions, except Share data, unless otherwise specified	Apr. 30, 2012	Dec. 31, 2013	Oct. 24, 2012	Apr. 30, 2012	Dec. 31, 2013	Nov. 12, 2013	Nov. 08, 2013	Nov. 30, 2011
				Common Class A [Member]	MAC Financial Holding Corporation and Subsidiaries [Member]	IPO [Member]	IPO [Member]	IPO [Member]
Class of Stock [Line Items]	'	'	'	'	'	'	'	'
Common stock offered and sold, (in shares)	'	'	'	55,000,000	'	'	2,100,000	2,400,000
Underwriting fee and other offering expense	$510	'	'	'	'	$28	'	'
Net stock issuance proceeds (percent)	93.00%	'	'	'	'	'	'	'
Proceeds from issuance of common stock, net of stock issuance costs	476	'	'	'	'	'	'	'
Repayments of long-term debt	'	'	'	'	35	'	'	'
Cash placed in operating account through time of GSE Approval	'	32	'	'	'	'	'	'
Purchaser discounts and placement fees	'	38.3	'	'	'	'	'	'
Purchase discount and placement fees paid in common stock	'	19.5	'	'	'	'	'	'
Purchase discount and placement fees paid in cash	'	18.8	'	'	'	'	'	'
Proceeds from sale of common stock placed in escrow	'	'	19.5	'	'	'	'	'
Maximum number of common stock shares granted to underwriters of IPO (in shares)	'	'	'	'	'	315,000	315,000	'
Maximum number of common stock shares granted to underwriters of IPO, exercise price (in dollars per share)	'	'	'	'	'	$13	$13	'
Proceeds from issuance initial public offering	'	'	'	'	'	$31.40	'	'
Underwriting fee and other offering expense (percent)	7.00%	'	'	'	'	6.00%	'	'

Acquisition_of_MAC_Details

Acquisition of MAC (Details) (MAC Financial Holding Corporation and Subsidiaries [Member], USD $)	Dec. 31, 2013	Dec. 31, 2012	Apr. 24, 2012
In Thousands, unless otherwise specified
MAC Financial Holding Corporation and Subsidiaries [Member]	'	'	'
Business Acquisition [Line Items]	'	'	'
Current assets	'	'	$52
Intangibles	'	'	1,590
Capitalized software	'	'	5,000
Goodwill	3,244	3,244	3,244
Subtotal	'	'	9,886
Current liabilities and deferred tax liabilities	'	'	-1,386
Estimated fair value of net assets acquired	'	'	$8,500

Acquisition_of_MAC_Narrative_D

Acquisition of MAC - Narrative (Details) (USD $)	7 Months Ended	12 Months Ended		1 Months Ended	3 Months Ended				1 Months Ended
	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Nov. 30, 2011	Dec. 31, 2012	Dec. 31, 2013	Apr. 24, 2012	Apr. 24, 2012	Nov. 30, 2011	Nov. 30, 2011
				MAC Financial Holding Corporation and Subsidiaries [Member]	MAC Financial Holding Corporation and Subsidiaries [Member]	MAC Financial Holding Corporation and Subsidiaries [Member]	MAC Financial Holding Corporation and Subsidiaries [Member]	MAC Financial Holding Corporation and Subsidiaries [Member]	MAC Financial Holding Corporation and Subsidiaries [Member]	MAC Financial Holding Corporation and Subsidiaries [Member]
								Operational Manuals [Member]	Warrant [Member]	Common Stock [Member]
Business Acquisition [Line Items]	'	'	'	'	'	'	'	'	'	'
Consideration paid	'	'	'	$8,500,000	'	'	'	'	'	'
Cash paid in acquisition	'	'	'	2,500,000	'	'	'	'	'	'
Common stock issued in connection with acquisition of subsidiaries (in shares)	'	'	'	'	'	'	'	'	2,500,000	3,500,000
Liabilities assumed in acquisition	'	'	'	1,300,000	'	'	'	'	'	'
Tax liabilities assumed in acquisition	'	'	'	100,000	'	'	'	'	'	'
Cash deposited in escrow	'	'	'	'	2,000,000	0	'	'	'	'
Intangibles	'	'	'	'	'	'	1,590,000	'	'	'
Operating manuals acquired	'	'	'	'	'	'	'	1,200,000	'	'
Loss on impairment	$0	$0	$1,200,000	'	$1,200,000	'	'	'	'	'

Investments_Narrative_Details

Investments - Narrative (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'	'
Unrealized losses	($7,319)	'
U.S. Treasury securities and obligations of U.S. government agencies [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Unrealized losses	-1,461	'
Cash and investments held with various state insurance departments	$7,000	$4,864

Investments_Fair_Values_and_Gr

Investments - Fair Values and Gross Unrealized Gains and Losses on Investments (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	$455,830	$4,863
Gross Unrealized Gains	272	1
Gross Unrealized (Losses)	-7,319	0
Fair Value	448,783	'
U.S. Treasury securities and obligations of U.S. government agencies [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	108,067	'
Gross Unrealized Gains	0	'
Gross Unrealized (Losses)	-1,461	'
Fair Value	106,606	'
Municipal bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	12,017	'
Gross Unrealized Gains	1	'
Gross Unrealized (Losses)	-85	'
Fair Value	11,933	'
Corporate debt securities [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	221,899	'
Gross Unrealized Gains	157	'
Gross Unrealized (Losses)	-4,799	'
Fair Value	217,257	'
Asset-backed securities [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	74,152	'
Gross Unrealized Gains	114	'
Gross Unrealized (Losses)	-974	'
Fair Value	73,292	'
Total bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	416,135	'
Gross Unrealized Gains	272	'
Gross Unrealized (Losses)	-7,319	'
Fair Value	409,088	'
Short-term investments [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	39,695	4,863
Gross Unrealized Gains	0	1
Gross Unrealized (Losses)	0	0
Fair Value	$39,695	$4,864

Investments_Scheduled_Maturiti

Investments - Scheduled Maturities (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]	'	'
Amortized Cost, Due in one year or less	$0	'
Amortized Cost, Due after one through five years	260,855	'
Amortized Cost, Due after five through ten years	65,687	'
Amortized Cost, Due after ten years	15,441	'
Amortized Cost, Total Investments	455,830	4,863
Available-for-sale Securities, Debt Maturities, Single Maturity Date [Abstract]	'	'
Fair Value, Due in one year or less	0	'
Fair Value, Due after one through five years	257,501	'
Fair Value, Due after five through ten years	63,440	'
Fair Value Due after ten years	14,855	'
Fair Value, Total Investments	448,783	'
Asset-backed securities [Member]	'	'
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]	'	'
Amortized Cost, Total Investments	74,152	'
Available-for-sale Securities, Debt Maturities, Single Maturity Date [Abstract]	'	'
Fair Value, Total Investments	73,292	'
Total bonds [Member]	'	'
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]	'	'
Amortized Cost, Total Investments	416,135	'
Available-for-sale Securities, Debt Maturities, Single Maturity Date [Abstract]	'	'
Fair Value, Total Investments	$409,088	'

Investments_Net_Realized_Inves

Investments - Net Realized Investment (Losses) Gains on Investments (Details) (USD $)	3 Months Ended								7 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Net realized investment gains	$14	($308)	$452	$28	$0	$0	$0	$0	$0	$186	$0
Corporate debt securities [Member]	'	'	'	'	'	'	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Net realized investment gains	'	'	'	'	'	'	'	'	'	323	'
U.S. Treasury securities and obligations of U.S. government agencies [Member]	'	'	'	'	'	'	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Net realized investment gains	'	'	'	'	'	'	'	'	'	-87	'
Asset-backed securities [Member]	'	'	'	'	'	'	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Net realized investment gains	'	'	'	'	'	'	'	'	'	($50)	'

Investments_Unrealized_Losses_

Investments - Unrealized Losses (Details) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'
Fair Value, Less than 12 Months	$357,460
Unrealized Losses, Less than 12 Months	-7,319
Fair Value, 12 Months or Greater	0
Unrealized Losses, 12 Months or Greater	0
Fair Value, Total	357,460
Unrealized Losses	-7,319
U.S. Treasury securities and obligations of U.S. government agencies [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Fair Value, Less than 12 Months	106,606
Unrealized Losses, Less than 12 Months	-1,461
Fair Value, 12 Months or Greater	0
Unrealized Losses, 12 Months or Greater	0
Fair Value, Total	106,606
Unrealized Losses	-1,461
Municipal bonds [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Fair Value, Less than 12 Months	4,915
Unrealized Losses, Less than 12 Months	-85
Fair Value, 12 Months or Greater	0
Unrealized Losses, 12 Months or Greater	0
Fair Value, Total	4,915
Unrealized Losses	-85
Corporate debt securities [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Fair Value, Less than 12 Months	187,714
Unrealized Losses, Less than 12 Months	-4,799
Fair Value, 12 Months or Greater	0
Unrealized Losses, 12 Months or Greater	0
Fair Value, Total	187,714
Unrealized Losses	-4,799
Asset-backed securities [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Fair Value, Less than 12 Months	58,225
Unrealized Losses, Less than 12 Months	-974
Fair Value, 12 Months or Greater	0
Unrealized Losses, 12 Months or Greater	0
Fair Value, Total	58,225
Unrealized Losses	($974)

Investments_Net_Investment_Inc

Investments - Net Investment Income (Details) (USD $)	7 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Investment income	$0	$5,291	$6
Investment expenses	0	-483	0
Net Investment Income	0	4,808	6
Fixed maturities [Member]	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Investment income	0	5,289	4
Cash equivalents [Member]	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Investment income	0	0	2
Other [Member]	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Investment income	$0	$2	$0

Fair_Value_of_Financial_Instru2

Fair Value of Financial Instruments - Narrative (Details) (Significant Unobservable Inputs (Level 3) [Member], USD $)	12 Months Ended
	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'
Volatility Assumption	39.00%
Warrant Liability [Member]	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'
Share Price (in dollars per share)	12.73
Risk free rate	2.25%
Expected term	'6 years 6 months 29 days
Expected dividend rate	0.00%

Fair_Value_of_Financial_Instru3

Fair Value of Financial Instruments - Assets and Liabilities at Fair Value (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	$448,783	'
Warrant liability, at fair value	6,371	4,842
Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	55,929	526,194
Total Assets	465,017	531,058
Warrant liability, at fair value	6,371	4,842
Financial and Nonfinancial Liabilities, Fair Value Disclosure	6,371	4,842
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	55,929	526,194
Total Assets	105,413	531,058
Warrant liability, at fair value	0	0
Financial and Nonfinancial Liabilities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	0	0
Total Assets	359,604	0
Warrant liability, at fair value	0	0
Financial and Nonfinancial Liabilities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	0	0
Total Assets	0	0
Warrant liability, at fair value	6,371	4,842
Financial and Nonfinancial Liabilities, Fair Value Disclosure	6,371	4,842
U.S. Treasury securities and obligations of U.S. government agencies [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	106,606	'
U.S. Treasury securities and obligations of U.S. government agencies [Member] | Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	106,606	4,864
U.S. Treasury securities and obligations of U.S. government agencies [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	49,484	4,864
U.S. Treasury securities and obligations of U.S. government agencies [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	57,122	0
U.S. Treasury securities and obligations of U.S. government agencies [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	0	0
Municipal bonds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	11,933	'
Municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	11,933	'
Municipal bonds [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	0	'
Municipal bonds [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	11,933	'
Municipal bonds [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	0	'
Corporate debt securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	217,257	'
Corporate debt securities [Member] | Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	217,257	'
Corporate debt securities [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	0	'
Corporate debt securities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	217,257	'
Corporate debt securities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	0	'
Asset-backed securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	73,292	'
Asset-backed securities [Member] | Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	73,292	'
Asset-backed securities [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	0	'
Asset-backed securities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	73,292	'
Asset-backed securities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale Securities	$0	'

Fair_Value_of_Financial_Instru4

Fair Value of Financial Instruments - Rollforward of Level 3 (Details) (Significant Unobservable Inputs (Level 3) [Member], USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013
In Thousands, unless otherwise specified			Warrant Liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'	'
Beginning balance	$6,371	$4,842	'
Change in fair value of warrant liability included in earnings	'	'	1,529
Ending balance	$6,371	$4,842	'

Software_and_Equipment_Details

Software and Equipment (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]	'	'
Less accumulated amortization and depreciation	($5,947)	($3)
Software and equipment, net	8,876	7,550
Software [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property plant and equipment	14,140	7,268
Equipment [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property plant and equipment	542	285
Leasehold Improvements [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property plant and equipment	$141	$0

Software_and_Equipment_Narrati

Software and Equipment - Narrative (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Apr. 24, 2012
			MAC Financial Holding Corporation and Subsidiaries [Member]
Property, Plant and Equipment [Line Items]	'	'	'
Capitalized software	'	'	$5,000
Depreciation and amortization	$5,900	$3	'

Intangible_Assets_and_Goodwill2

Intangible Assets and Goodwill (Details) (USD $)	7 Months Ended	12 Months Ended		3 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2013	Apr. 24, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
				MAC Financial Holding Corporation and Subsidiaries [Member]	MAC Financial Holding Corporation and Subsidiaries [Member]	MAC Financial Holding Corporation and Subsidiaries [Member]	MAC Financial Holding Corporation and Subsidiaries [Member]	MAC Financial Holding Corporation and Subsidiaries [Member]	MAC Financial Holding Corporation and Subsidiaries [Member]	MAC Financial Holding Corporation and Subsidiaries [Member]
							State licenses [Member]	State licenses [Member]	GSE Approvals [Member]	GSE Approvals [Member]
Indefinite-lived Intangible Assets [Line Items]	'	'	'	'	'	'	'	'	'	'
Goodwill	'	'	'	$3,244	$3,244	$3,244	'	'	'	'
Intangible assets	'	'	'	'	'	'	260	260	130	130
Goodwill and other indefinite lived intangible assets	'	3,634	3,634	390	3,634	'	'	'	'	'
Loss on impairment	$0	$0	$1,200	$1,200	'	'	'	'	'	'

Commitments_and_Contingencies_1

Commitments and Contingencies - Future Minimum Lease Payments (Details) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Commitments and Contingencies Disclosure [Abstract]	'
2014	$1,570
2015	1,670
2016	1,741
2017	1,489
Totals	$6,470

Commitments_and_Contingencies_2

Commitments and Contingencies - Narrative (Details) (USD $)

12 Months Ended

12 Months Ended

4 Months Ended

12 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Oct. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Sep. 02, 2013

Dec. 31, 2013

Dec. 31, 2013

sqft

NMI Re One [Member]

Fannie Mae and Freddie Mac [Member]

Fannie Mae and Freddie Mac [Member]

Fannie Mae [Member]

Fannie Mae [Member]

Fannie Mae [Member]

Maximum [Member]

Maximum [Member]

NMI Re One [Member]

loan

Fannie Mae and Freddie Mac [Member]

Compliance with Regulatory Capital Requirements for Mortgage Companies [Line Items]

'

'

'

'

'

'

'

'

'

'

'

Minimum capitalization requirement period

'3 years

'

'

'

'

'

'

'

'

'

'

Capital required to be capitalized

'

'

'

'

$200,000,000

$10,000,000

'

'

'

'

'

Minimum capital required

'

'

'

'

150,000,000

'

'

'

'

'

'

Risk-to-capital

'

'

'

'

20

'

18

18

'

25

15

Statutory capital and surplus required, period

'

'

'

'

'3 years

'

'

'

'

'

'

Statutory capital and surplus required, no declaration or dividend payment period

'

'

'

'

'3 years

'

'

'

'

'

'

Statutory capital and surplus required, requirement to not enter in capital support agreement period

'

'

'

'

'3 years

'

'

'

'

'

'

Statutory capital and surplus required, agreement to not enter in to reinsurance risk period

'

'

'

'

'3 years

'

'

'

'

'

'

Shareholder percent provision regarding underwriting policies

5.00%

'

'

'

'

'

'

'

'

'

'

Mortgage insurance pool agreement, number of loans

'

'

'

'

'

'

22,000

'

'

'

'

Mortgage insurance pool agreement, aggregate unpaid principal balance

'

'

'

'

'

'

5,200,000,000

5,200,000,000

'

'

'

Mortgage insurance pool agreement, expected term

'

'

'

'

'

'

'

'10 years

'

'

'

Pool risk-in-force

93,090,000

[1]

'

'

25,171,000

[1]

'

'

'

'

93,100,000

[1]

'

'

Office facility lease, term of contract

'2 years

'

'

'

'

'

'

'

'

'

'

Rent expense

$800,000

$200,000

'

'

'

'

'

'

'

'

'

Additional Square Feet of Furnished Office Space under Amended Lease Terms

'

'

23,000

'

'

'

'

'

'

'

'

[1]

Pool risk-in-force as shown in the table above is equal to the aggregate stop loss less a deductible.

Income_Taxes_Deferred_Tax_Asse

Income Taxes - Deferred Tax Asset (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Deferred Tax Asset, Gross [Abstract]	'	'
Capitalized start-up costs	$2,579	$21,796
Stock compensation	14,701	'
Unrealized loss on investments	7,047	'
Net operating loss carry forwards	65,276	7,307
Other	10,118	'
Total gross deferred tax assets	99,721	29,103
Less: valuation allowance	-94,497	-24,103
Total deferred tax assets	5,224	5,000
Deferred tax asset:	'	'
Capitalized start-up costs	903	7,411
Stock compensation	5,990	'
Unrealized loss on investments	2,694	'
Net operating loss carry forwards	24,602	2,484
Other	3,760	'
Total gross deferred tax assets	37,949	9,895
Less: valuation allowance	-35,778	-8,195
Total deferred tax assets	2,171	1,700
Deferred Tax Liability, Gross [Abstract]	'	'
Capitalized software	-5,008	-5,000
Intangible assets	-390	-390
Other	-216	'
Total deferred tax liabilities	-5,614	-5,390
Net deferred income tax liability	-390	-390
Deferred tax liability:	'	'
Capitalized software	-2,095	-1,700
Intangible assets	-133	-133
Other	-76	'
Total deferred tax liabilities	-2,304	-1,833
Net deferred income tax liability	($133)	($133)

Income_Taxes_Narrative_Details

Income Taxes - Narrative (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Income Tax Contingency [Line Items]	'	'
Deferred tax liabilities, gross	$133,000	$133,000
Taxes paid related to net share settlement of equity awards	1,500,000	'
Loss carry forwards subject to expiration	7,300,000	'
Valuation allowance	35,778,000	8,195,000
Annual Limitation Through Year Three [Member]	'	'
Income Tax Contingency [Line Items]	'	'
Loss carry forwards subject to expiration	800,000	'
Annual Limitations After Year Three [Member]	'	'
Income Tax Contingency [Line Items]	'	'
Loss carry forwards subject to expiration	300,000	'
Domestic Tax Authority [Member]	'	'
Income Tax Contingency [Line Items]	'	'
Operating loss carryforwards	65,300,000	'
State and Local Jurisdiction [Member]	'	'
Income Tax Contingency [Line Items]	'	'
Operating loss carryforwards	$30,500,000	'

Income_Taxes_Income_Tax_Reconc

Income Taxes - Income Tax Reconciliation (Details)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]	'	'
Federal statutory income tax rate	35.00%	35.00%
Loss on impairment	0.00%	-1.48%
Prior year adjustment	3.52%	1.66%
Other	1.66%	-1.00%
Valuation allowance	-40.18%	-28.00%
Purchase accounting adjustment	0.00%	-6.18%
Effective income tax rate	0.00%	0.00%

ShareBased_Compensation_Stock_

Share-Based Compensation - Stock Option Activity (Details) (The 2012 Stock Incentive Plan [Member], USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
The 2012 Stock Incentive Plan [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]	'	'
Options beginning balance (in shares)	2,547	0
Options granted (in shares)	532	2,829
Less: Options forfeited (in shares)	-15	-282
Less: Options canceled (in shares)	-1	0
Options ending balance (in shares)	3,063	2,547
Weighted Average Grant Date Fair Value per Share	'	'
Options beginning balance (in dollars per share)	$10	$0
Options granted (in dollars per share)	$11.78	$10
Less: Options forfeited (in dollars per share)	$10	$10
Less: Options canceled (in dollars per share)	$10	$0
Options beginning balance (in dollars per share)	$10.31	$10
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]	'	'
Options beginning balance (in dollars per share)	$3.86	$0
Options granted (in dollars per share)	$4.57	$3.87
Less: Options forfeited (in dollars per share)	$3.84	$3.88
Less: Options canceled (in dollars per share)	$3.84	$0
Options ending balance (in dollars per share)	$3.98	$3.86

ShareBased_Compensation_Stock_1

Share-Based Compensation - Stock Options, Valuation Assumptions (Details) (The 2012 Stock Incentive Plan [Member], Stock Options [Member])	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Expected life	'6 years	'6 years
Dividend yield	0.00%	0.00%
Expected stock price volatility	39.00%	39.00%
Projected forfeiture rate	1.00%	1.00%
Minimum [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Risk free interest rate	0.98%	0.85%
Maximum [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Risk free interest rate	1.12%	1.12%

ShareBased_Compensation_Restri

Share-Based Compensation - Restricted Stock Units Activity (Details) (The 2012 Stock Incentive Plan [Member], Restricted Stock Units [Member], USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
The 2012 Stock Incentive Plan [Member] | Restricted Stock Units [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]	'	'
Restricted Stock beginning balance (in shares)	1,429	0
Restricted stock units granted (in shares)	76	1,667
Less: Restricted stock units vested (in shares)	-263	'
Less: Restricted stock units forfeited (in shares)	0	-238
Restricted Stock beginning balance (in shares)	1,242	1,429
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]	'	'
Restricted Stock beginning balance (in dollars per share)	$7.35	$0
Restricted Stock Units Granted (in dollars per share)	$12.03	$7.35
Less: Restricted Stock Units Vested (in dollars per share)	$6.79	'
Less: Restricted Stock Units Forfeited (in dollars per share)	$0	$7.35
Restricted Stock ending balance (in dollars per share)	$7.75	$7.35

ShareBased_Compensation_Restri1

Share-Based Compensation - Restricted Stock Units, Valuation Assumptions (Details) (The 2012 Stock Incentive Plan [Member], Restricted Stock Units [Member])	12 Months Ended
	Dec. 31, 2013
The 2012 Stock Incentive Plan [Member] | Restricted Stock Units [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Expected life	'5 years
Risk free interest rate	0.86%
Dividend yield	0.00%
Expected stock price volatility	39.00%
Projected forfeiture rate	1.00%

ShareBased_Compensation_Narrat

Share-Based Compensation - Narrative (Details) (USD $)	0 Months Ended	1 Months Ended	3 Months Ended	12 Months Ended
In Millions, except Share data, unless otherwise specified	Apr. 05, 2013	Feb. 28, 2013	Jun. 30, 2013	Dec. 31, 2013	Dec. 31, 2012	Apr. 16, 2012	Dec. 31, 2011
				simulation
Stock Options [Member]	'	'	'	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'	'	'
Expiration period	'	'	'	'10 years	'	'	'
Restricted stock vesting period	'	'	'	'3 years	'	'	'
The 2012 Stock Incentive Plan [Member]	'	'	'	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'	'	'
Number of shares authorized to be reserved for issuance (in shares)	'	'	'	'	'	5,500,000	'
Number of options vested (in shares)	'	'	'	743,000	'	'	'
Weighted average exercise price for options vested (in dollars per share)	'	'	'	$10	'	'	'
Weighted average remaining contractual term	'	'	'	'8 years 4 months 24 days	'	'	'
Options vested aggregate value	'	'	'	$2	'	'	'
Weighted average remaining contractual life of options outstanding	'	'	'	'8 years 6 months 15 days	'	'	'
Total unrecognized compensation cost related to non-vested stock options	'	'	'	3.6	'	'	'
Compensation related to non-vested awards, weighted-average period for recognition	'	'	'	'8 months 19 days	'	'	'
The 2012 Stock Incentive Plan [Member] | Stock Options [Member]	'	'	'	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'	'	'
Number of shares authorized to be reserved for issuance (in shares)	'	'	'	'	'	3,850,000	'
The 2012 Stock Incentive Plan [Member] | Restricted Stock Units [Member]	'	'	'	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'	'	'
Number of shares authorized to be reserved for issuance (in shares)	'	'	'	'	'	1,650,000	'
Expiration period	'	'	'	'10 years	'	'	'
Compensation related to non-vested awards, weighted-average period for recognition	'	'	'	'9 months 7 days	'	'	'
Modification to vesting terms, number of restricted stock units affected (in shares)	'	400,000	'	'	'	'	'
Restricted stock units outstanding (in shares)	'	'	'	1,242,000	1,429,000	'	0
Restricted stock units outstanding, number of shares subject to both market and service conditions (in shares)	'	'	'	525,223	'	'	'
Restricted stock units outstanding, number of shares subject to only service conditions (in shares)	'	'	'	723,427	'	'	'
Number of simulations	'	'	'	150,000	'	'	'
Vesting percentage subject to both market and service conditions, annual vesting percentage	'	'	'	33.00%	'	'	'
Weighted average remaining contractual life of RSUs outstanding	'	'	'	'4 years 0 months 11 days	'	'	'
Total unrecognized compensation cost related to non-vested restricted stock units	'	'	'	4.3	'	'	'
Restricted stock units, number of shares containing a market condition vested (in shares)	263,000	'	'	'	'	'	'
Acceleration of compensation expense	'	'	$1.10	'	'	'	'
Minimum [Member] | The 2012 Stock Incentive Plan [Member] | Restricted Stock Units [Member]	'	'	'	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'	'	'
Restricted stock vesting period	'	'	'	'1 year	'	'	'
Maximum [Member] | The 2012 Stock Incentive Plan [Member] | Restricted Stock Units [Member]	'	'	'	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'	'	'
Restricted stock vesting period	'	'	'	'3 years	'	'	'

Warrants_Details

Warrants (Details) (USD $)	Apr. 24, 2012	Dec. 31, 2011	Apr. 24, 2012
In Millions, except Share data in Thousands, unless otherwise specified		FBR Capital Markets and Co. [Member]	MAC Financial Holding Corporation and Subsidiaries [Member]
		Line of Credit [Member]
Line of Credit Facility [Line Items]	'	'	'
Line of credit facility, borrowing capacity	'	$1.50	'
Exercise price of warrants (in dollars per warrant)	10	'	10
Warrants issued (in shares)	314	'	678
Warrants value	$1.60	'	$3.50

Statutory_Information_Statutor

Statutory Information - Statutory Income (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Insurance [Abstract]	'	'	'
Statutory net loss	($33,307)	($18)	$0
Statutory surplus	189,698	220,004	0
Contingency reserve	$2,314	$0	$0

Statutory_Information_Narrativ

Statutory Information - Narrative (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	18-May-11	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013
	state				Subsidiaries [Member]	Maximum [Member]	WISCONSIN [Member]	Fannie Mae and Freddie Mac [Member]	Fannie Mae and Freddie Mac [Member]	Fannie Mae [Member]
							Maximum [Member]		Maximum [Member]
Statutory Accounting Practices [Line Items]	'	'	'	'	'	'	'	'	'	'
Number of states which require minimum amount of statutory capital relative to risk in force	15	'	'	'	'	'	'	'	'	'
Risk-to-capital	'	'	'	'	'	25	18	20	15	18
Potential risk In force to capital, ratio	'	'	'	'	'	'	25	'	'	'
Statutory capital and surplus required	'	'	'	'	'	'	'	$150,000,000	'	'
Statutory capital and surplus required, period	'	'	'	'	'	'	'	'3 years	'	'
Mortgage insurance, percentage of indebtedness on single loan	25.00%	'	'	'	'	'	'	'	'	'
Shareholders' equity	463,217,000	488,748,000	-1,349,000	0	193,000,000	'	'	'	'	'
Investment in subsidiaries, at equity in net assets	$276,000,000	'	'	'	'	'	'	'	'	'
Ordinary dividends, restriction with regards to capital surplus	10.00%	'	'	'	'	'	'	'	'	'

Statutory_Information_Risk_to_

Statutory Information - Risk to Capital (Details) (USD $)	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Pool risk-in-force	'		'	'
Direct	$93,090	[1]	'	'
Assumed	25,171	[1]	'	'
Ceded	-25,171	[1]	'	'
Total pool risk-in-force	93,090	[1]	'	'
Primary risk-in-force	'		'	'
Direct	36,516		'	'
Assumed	2,637		'	'
Ceded	-2,637		'	'
Total primary risk-in-force	36,516		'	'
Total risk-in-force	129,606		'	'
Total statutory policyholders' position	189,698		220,004	0
Statutory contingency reserve	2,314		'	'
Total statutory policyholders' position	192,012		'	'
Risk to capital ratio	0.7	[2]	'	'
NMIC [Member]	'		'	'
Pool risk-in-force	'		'	'
Direct	93,090	[1]	'	'
Assumed	0	[1]	'	'
Ceded	-25,171	[1]	'	'
Total pool risk-in-force	67,919	[1]	'	'
Primary risk-in-force	'		'	'
Direct	36,516		'	'
Assumed	0		'	'
Ceded	-2,637		'	'
Total primary risk-in-force	33,879		'	'
Total risk-in-force	101,798		'	'
Total statutory policyholders' position	180,310		'	'
Statutory contingency reserve	1,740		'	'
Total statutory policyholders' position	182,050		'	'
Risk to capital ratio	0.6	[2]	'	'
NMI Re One [Member]	'		'	'
Pool risk-in-force	'		'	'
Direct	0	[1]	'	'
Assumed	25,171	[1]	'	'
Ceded	0	[1]	'	'
Total pool risk-in-force	25,171	[1]	'	'
Primary risk-in-force	'		'	'
Direct	0		'	'
Assumed	2,637		'	'
Ceded	0		'	'
Total primary risk-in-force	2,637		'	'
Total risk-in-force	27,808		'	'
Total statutory policyholders' position	9,388		'	'
Statutory contingency reserve	574		'	'
Total statutory policyholders' position	$9,962		'	'
Risk to capital ratio	2.8	[2]	'	'
[1]	Pool risk-in-force as shown in the table above is equal to the aggregate stop loss less a deductible.
[2]	Represents total risk-in-force divided by statutory policyholders' position which is the metric by which the majority of state insurance regulators will assess our capital adequacy. Additionally, Fannie Mae requires us to maintain the greater of (a) the risk-to-capital requirements outlined in the January 2013 approval letter, or (b) a risk-to-capital ratio of 18:1 on primary business plus statutory capital equal to the amount of net risk-in-force of the pool.

Quarterly_Financial_Data_Unaud2

Quarterly Financial Data (Unaudited) (Details) (USD $)	3 Months Ended																7 Months Ended	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Quarterly Financial Information Disclosure [Abstract]	'		'		'		'		'		'		'		'		'	'		'		'
Net premiums written	$3,058		$482		$1		$0		$0		$0		$0		$0		$0	$3,541		$0		'
Net premiums earned	1,612		482		1		0		0		0		0		0		0	2,095		0		'
Net investment income	1,472		1,519		1,407		410		5		1		0		0		0	4,808		6		'
Net realized investment gains	14		-308		452		28		0		0		0		0		0	186		0		'
(Loss) Gain from change in fair value of warrant liability	-918		469		-1,115		35		278		0		0		0		0	-1,529		278		'
Insurance claims and claims expenses	0		0		0		0		0		0		0		0		0	0		0		'
Amortization of deferred policy acquisition costs	1		0		0		0		0		0		0		0		0	1		0		'
Other underwriting and operating expenses	15,263		16,035		17,019		12,426		13,079		8,114		6,196		386		1,349	60,743		27,775		'
Net loss	($13,084)		($13,873)		($16,274)		($11,953)		($12,796)		($8,113)		($6,196)		($386)		($1,349)	($55,184)		($27,491)		($27,491)
Basic and Diluted loss per share (in dollars per share)	($0.23)	[1]	($0.25)	[1]	($0.29)	[1]	($0.22)	[1]	($0.23)	[1]	($0.15)	[1]	($0.15)	[1]	($3,860)	[1]	($13,490)	($0.99)	[1]	($0.73)	[1]	'
Weighted average common shares outstanding (in shares)	57,238,730	[1]	55,637,480	[1]	55,629,932	[1]	55,500,100	[1]	55,500,100	[1]	55,500,100	[1]	40,252,847	[1]	100	[1]	100	56,005,326	[1]	37,909,936	[1]	'
[1]	Due to the use of weighted average shares outstanding when calculating earnings per share, the sum of quarterly per share data may not equal the per share data for the year.

SCHEDULE_I_SUMMARY_OF_INVESTME1

SCHEDULE I - SUMMARY OF INVESTMENTS (Details) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]	'
Amortized Cost	$233,023
Fair Value	229,064
Amount Reflected on Balance Sheet	229,064
U.S. Treasury securities and obligations of U.S. government agencies [Member]	'
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]	'
Amortized Cost	58,251
Fair Value	57,421
Amount Reflected on Balance Sheet	57,421
Municipal bonds [Member]	'
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]	'
Amortized Cost	5,259
Fair Value	5,204
Amount Reflected on Balance Sheet	5,204
Corporate debt securities [Member]	'
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]	'
Amortized Cost	130,499
Fair Value	127,928
Amount Reflected on Balance Sheet	127,928
Asset-backed securities [Member]	'
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]	'
Amortized Cost	39,014
Fair Value	38,511
Amount Reflected on Balance Sheet	$38,511

SCHEDULE_II_FINANCIAL_INFORMAT1

SCHEDULE II - FINANCIAL INFORMATION OF REGISTRANT - Balance Sheet (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	18-May-11
In Thousands, unless otherwise specified
Assets	'	'	'	'
Investments, available-for-sale	$409,088	$4,864	'	'
Cash and cash equivalents	55,929	485,855	0	0
Restricted cash	0	40,338	'	'
Investment in subsidiaries, at equity in net assets	276,000	'	'	'
Accrued investment income	2,001	6	'	'
Prepaid expenses	1,519	417	'	'
Software and equipment, net	8,876	7,550	'	'
Other assets	63	104	'	'
Total Assets	481,219	542,768	'	'
Liabilities	'	'	'	'
Accounts payable and accrued expenses	10,052	8,707	'	'
Placement fee payable	0	38,305	'	'
Purchase consideration payable	0	2,033	'	'
Warrant liability, at fair value	6,371	4,842	'	'
Total Liabilities	18,002	54,020	'	'
Equity [Abstract]	'	'	'	'
Additional paid-in capital	553,707	517,032	'	'
Accumulated other comprehensive (loss) income	-7,047	1	'	'
Accumulated deficit	-84,024	-28,840	'	'
Total Shareholders' Equity	463,217	488,748	-1,349	0
Total Liabilities and Shareholders' Equity	481,219	542,768	'	'
Parent [Member]	'	'	'	'
Assets	'	'	'	'
Investments, available-for-sale	229,064	0	'	'
Cash and cash equivalents	36,433	270,717	0	0
Restricted cash	0	40,338	'	'
Investment in subsidiaries, at equity in net assets	193,242	228,612	'	'
Accrued investment income	1,038	0	'	'
Prepaid expenses	1,519	417	'	'
Due from affiliates, net	10,565	0	'	'
Software and equipment, net	7,574	2,444	'	'
Other assets	61	107	'	'
Total Assets	479,496	542,635	'	'
Liabilities	'	'	'	'
Accounts payable and accrued expenses	9,908	8,707	'	'
Placement fee payable	0	38,305	'	'
Purchase consideration payable	0	2,033	'	'
Warrant liability, at fair value	6,371	4,842	'	'
Total Liabilities	16,279	53,887	'	'
Equity [Abstract]	'	'	'	'
Additional paid-in capital	553,707	517,032	'	'
Accumulated other comprehensive (loss) income	-7,047	1	'	'
Accumulated deficit	-84,024	-28,840	'	'
Total Shareholders' Equity	463,217	488,748	'	'
Total Liabilities and Shareholders' Equity	479,496	542,635	'	'
Common Class A [Member]	'	'	'	'
Equity [Abstract]	'	'	'	'
Common stock, shares outstanding	581	553	'	'
Common Class A [Member] | Parent [Member]	'	'	'	'
Equity [Abstract]	'	'	'	'
Common stock, shares outstanding	581	553	'	'
Common Class B [Member]	'	'	'	'
Equity [Abstract]	'	'	'	'
Common stock, shares outstanding	0	2	'	'
Common Class B [Member] | Parent [Member]	'	'	'	'
Equity [Abstract]	'	'	'	'
Common stock, shares outstanding	$0	$2	'	'

SCHEDULE_II_FINANCIAL_INFORMAT2

SCHEDULE II - FINANCIAL INFORMATION OF REGISTRANT -(Parenthetical) (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Common Class A [Member]	'	'
Common stock, par value (in dollars per share)	$0.01	$0.01
Common stock, shares issued	58,052,480	55,250,100
Common stock, shares outstanding	58,052,480	55,250,100
Common stock, shares authorized	250,000,000	250,000,000
Common Class B [Member]	'	'
Common stock, par value (in dollars per share)	$0.01	$0.01
Common stock, shares issued	0	250,000
Common stock, shares outstanding	0	250,000
Common stock, shares authorized	250,000	250,000
Parent [Member] | Common Class A [Member]	'	'
Common stock, par value (in dollars per share)	$0.01	$0.01
Common stock, shares issued	58,052,480	55,250,100
Common stock, shares outstanding	58,052,480	55,250,100
Common stock, shares authorized	250,000,000	250,000,000
Parent [Member] | Common Class B [Member]	'	'
Common stock, par value (in dollars per share)	$0.01	$0.01
Common stock, shares issued	0	250,000
Common stock, shares outstanding	0	250,000
Common stock, shares authorized	250,000	250,000

SCHEDULE_II_FINANCIAL_INFORMAT3

SCHEDULE II - FINANCIAL INFORMATION OF REGISTRANT - Income Statement (Details) (USD $)

3 Months Ended

7 Months Ended

12 Months Ended

In Thousands, unless otherwise specified

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Assets

'

'

'

'

'

'

'

'

'

'

'

'

Net investment income

$1,472

$1,519

$1,407

$410

$5

$1

$0

$0

$0

$4,808

$6

'

Net realized investment gains

14

-308

452

28

0

0

0

0

0

186

0

'

(Loss) Gain from change in fair value of warrant liability

-918

469

-1,115

35

278

0

0

0

0

-1,529

278

'

Total Revenues

'

'

'

'

'

'

'

'

0

5,560

284

'

Expenses

'

'

'

'

'

'

'

'

'

'

'

'

Other underwriting and operating expenses

15,263

16,035

17,019

12,426

13,079

8,114

6,196

386

1,349

60,743

27,775

'

Total Expenses

'

'

'

'

'

'

'

'

1,349

60,744

27,775

'

Net Loss

-13,084

-13,873

-16,274

-11,953

-12,796

-8,113

-6,196

-386

-1,349

-55,184

-27,491

-27,491

Parent [Member]

'

'

'

'

'

'

'

'

'

'

'

'

Assets

'

'

'

'

'

'

'

'

'

'

'

'

Net investment income

'

'

'

'

'

'

'

'

0

2,758

2

'

Net realized investment gains

'

'

'

'

'

'

'

'

0

188

0

'

(Loss) Gain from change in fair value of warrant liability

'

'

'

'

'

'

'

'

0

-1,529

278

'

Total Revenues

'

'

'

'

'

'

'

'

0

1,417

280

'

Expenses

'

'

'

'

'

'

'

'

'

'

'

'

Other underwriting and operating expenses

'

'

'

'

'

'

'

'

1,349

24,319

26,575

'

Total Expenses

'

'

'

'

'

'

'

'

1,349

24,319

26,575

'

Equity in net loss of subsidiaries

'

'

'

'

'

'

'

'

0

-32,282

-1,196

'

Net Loss

'

'

'

'

'

'

'

'

($1,349)

($55,184)

($27,491)

'

SCHEDULE_II_FINANCIAL_INFORMAT4

SCHEDULE II - FINANCIAL INFORMATION OF REGISTRANT - Cash Flow Statement (Details) (USD $)	7 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net Cash Provided by (Used in) Operating Activities [Abstract]	'	'	'	'
Net loss	($1,349,000)	($55,184,000)	($27,491,000)	($27,491,000)
Adjustments to reconcile net loss to net cash used in operating activities:	'	'	'	'
Share-based compensation expense	0	10,367,000	6,115,000	'
Warrants issued in connection with line of credit	0	0	1,620,000	'
Loss (gain) from change in fair value of warrant liability	0	1,529,000	-278,000	'
Net realized investment gains	0	-186,000	0	'
Depreciation and other amortization	0	8,116,000	3,000	'
Accrued investment income	0	-2,001,000	-6,000	'
Changes in operating assets and liabilities:	'	'	'	'
Prepaid expenses	-183,000	-1,102,000	-234,000	'
Other assets	-27,000	46,000	-78,000	'
Accounts payable and accrued expenses	1,354,000	767,000	4,553,000	'
Net Cash Used in Operating Activities	-205,000	-36,311,000	-14,596,000	'
Cash Flows from Investing Activities	'	'	'	'
Purchase of fixed maturities, available-for-sale	0	-559,875,000	0	'
Proceeds from sale of fixed maturities, available-for-sale	0	141,754,000	0	'
Purchase of software and equipment	0	-6,692,000	-2,447,000	'
Acquisition of subsidiaries	0	0	-2,500,000	'
Net Cash Used in Investing Activities	0	-419,949,000	-9,809,000	'
Cash Flows from Financing Activities	'	'	'	'
(Payments) Proceeds on line of credit	205,000	0	-205,000	'
Issuance of common stock	0	27,912,000	510,465,000	'
Taxes paid related to net share settlement of equity awards	0	-1,578,000	0	'
Net Cash Provided by Financing Activities	205,000	26,334,000	510,260,000	'
Net (Decrease) Increase in Cash and Cash Equivalents	0	-429,926,000	485,855,000	'
Cash and Cash Equivalents, beginning of period	0	485,855,000	0	'
Cash and Cash Equivalents, end of period	0	55,929,000	485,855,000	0
Parent [Member]	'	'	'	'
Net Cash Provided by (Used in) Operating Activities [Abstract]	'	'	'	'
Net loss	-1,349,000	-55,184,000	-27,491,000	'
Adjustments to reconcile net loss to net cash used in operating activities:	'	'	'	'
Share-based compensation expense	0	10,367,000	6,115,000	'
Warrants issued in connection with line of credit	0	0	1,620,000	'
Loss (gain) from change in fair value of warrant liability	0	1,529,000	-278,000	'
Net realized investment gains	0	-188,000	0	'
Depreciation and other amortization	0	3,325,000	3,000	'
Accrued investment income	0	-1,038,000	-2,000	'
Changes in operating assets and liabilities:	'	'	'	'
Receivable from affiliates	0	-10,565,000	0	'
Prepaid expenses	-183,000	-1,102,000	-234,000	'
Other assets	-26,000	32,326,000	1,118,000	'
Accounts payable and accrued expenses	1,353,000	623,000	4,550,000	'
Net Cash Used in Operating Activities	-205,000	-19,907,000	-14,599,000	'
Cash Flows from Investing Activities	'	'	'	'
Capitalization of subsidiaries	0	0	-220,000,000	'
Purchase of fixed maturities, available-for-sale	0	-293,470,000	0	'
Proceeds from sale of fixed maturities, available-for-sale	0	59,454,000	0	'
Purchase of software and equipment	0	-6,695,000	-2,444,000	'
Acquisition of subsidiaries	0	0	-2,500,000	'
Net Cash Used in Investing Activities	0	-240,711,000	-224,944,000	'
Cash Flows from Financing Activities	'	'	'	'
(Payments) Proceeds on line of credit	205,000	0	0	'
Payment of financing debt	0	0	-205,000	'
Issuance of common stock	0	27,912,000	510,465,000	'
Taxes paid related to net share settlement of equity awards	0	-1,578,000	0	'
Net Cash Provided by Financing Activities	205,000	26,334,000	510,260,000	'
Net (Decrease) Increase in Cash and Cash Equivalents	0	-234,284,000	270,717,000	'
Cash and Cash Equivalents, beginning of period	0	270,717,000	0	'
Cash and Cash Equivalents, end of period	$0	$36,433,000	$270,717,000	$0

SCHEDULE_II_FINANCIAL_INFORMAT5

SCHEDULE II - FINANCIAL INFORMATION OF REGISTRANT - Supplemental Notes (Details) (Subsidiaries [Member], USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Subsidiaries [Member]	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'
Other underwriting and operating expenses	$32,500,000	$0	$0