Investments, Debt and Equity Securities [Abstract] Investments Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Insurance [Abstract] Statutory Information Insurance Disclosure [Text Block] Debt Disclosure [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Senior Secured Debt Senior Secured Debt [Member] Senior Secured Debt [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Credit Agreement Credit Agreement [Member] Credit Agreement [Member] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] Initial Eurodollar Annual Margin Initial Eurodollar Annual Margin [Member] Initial Eurodollar Annual Margin [Member] Eurodollar Eurodollar [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Debt instrument term Debt Instrument, Term Debt instrument, face amount Debt Instrument, Face Amount Variable rate floor Debt Instrument, Variable Interest Rate Floor Debt Instrument, Variable Interest Rate Floor Basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Periodic payment of principal Debt Instrument, Periodic Payment, Principal Term loan Long-term Debt, Gross Debt issuance cost Debt Issuance Cost Percentage of debt discount Debt Discount (Premium), Percentage Debt Discount (Premium), Percentage Interest expense Interest Expense, Debt Debt instrument covenant, maximum debt-to-total capitalization ratio Debt Instrument, Covenant, Debt to Total Capitalization Ratio, Maximum Debt Instrument, Covenant, Debt to Total Capitalization Ratio, Maximum Debt instrument covenant, maximum risk-to-capital ratio Debt Instrument, Covenant, Risk to Capital Ratio, Maximum Debt Instrument, Covenant, Risk to Capital Ratio, Maximum Debt instrument covenant, minimum liquidity requirement Debt Instrument, Covenant, Liquidity Requirement, Minimum Debt Instrument, Covenant, Liquidity Requirement, Minimum Term Loan Debt Disclosure [Text Block] Document and Entity Information [Abstract] Document and Entity Information [Abstract] Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Document Type Document Type Document Period End Date Document Period End Date Amendment Flag Amendment Flag Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Line of Credit Facility [Table] Line of Credit Facility [Table] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Common Stock - Class A Common Class A [Member] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock - Class A Common Stock [Member] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Warrants issued (in shares) Class of Warrant or Right, Number of Securities Called by Warrants or Rights Right to purchase, number of shares per warrant Number Of Shares, Right To Purchase Per Warrant Number Of Shares, Right To Purchase Per Warrant Exercise price of warrants (in dollars per warrant) Class of Warrant or Right, Exercise Price of Warrants or Rights Warrants value Warrants and Rights Outstanding Number of warrants exercised during period Class of Warrant or Right, Number of Warrants Exercised During Period Class of Warrant or Right, Number of Warrants Exercised During Period Issuance of Class A shares of common stock as part of cashless exercise of warrants, shares Stock Issued During Period, Shares, Other Gain from settlement of warrants Gain (Loss) From Settlement of Warrants Gain (Loss) From Settlement of Warrants Schedule of Future Principal Payments Schedule of Maturities of Long-term Debt [Table Text Block] Gross realized investment gains Available-for-sale Securities, Gross Realized Gains Gross realized investment losses Available-for-sale Securities, Realized Losses, Excluding Other than Temporary Impairments Net realized investment (losses) gains Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments Reconciliation of Liability for Insurance Claims and Claims Expenses Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization and Basis of Presentation Business Description and Basis of Presentation [Text Block] Fair Value Disclosures [Abstract] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Significant Unobservable Inputs (Level 3) Fair Value, Inputs, Level 3 [Member] Liability Class [Axis] Liability Class [Axis] Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Warrant Liability Warrant Liability [Member] Warrant Liability [Member] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Beginning balance Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value Change in fair value of warrant liability included in earnings Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings Issuance of common stock on warrant exercise Warrant Liability, Reduction, Transferred to Equity Warrant Liability, Reduction, Transferred to Equity Gain on settlement of warrants Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements Ending balance Fair Value Measurements, Recurring and Nonrecurring Fair Value Measurements, Recurring and Nonrecurring [Table Text Block] Roll-Forward of Level 3 Liabilities Measured at Fair Value Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Income Statement [Abstract] Revenues Revenues [Abstract] Net premiums written Premiums Written, Net Increase in unearned premiums (Increase) Decrease in Unearned Premiums, Net Net premiums earned Premiums Earned, Net Net investment income Net Investment Income Net realized investment (losses) gains Available-for-sale Securities, Gross Realized Gain (Loss) Other revenues Other Revenue, Net Total revenues Revenues Expenses Costs and Expenses [Abstract] Insurance claims and claims expenses Policyholder Benefits and Claims Incurred, Net, Property, Casualty and Liability Underwriting and operating expenses Other Cost and Expense, Operating Total expenses Costs and Expenses Other (expense) income Other Income and Expenses [Abstract] Gain from change in fair value of warrant liability Gain (Loss) on Change in Fair Value of Warrant Liability Gain (Loss) on Change in Fair Value of Warrant Liability Total other (expense) income Other Nonoperating Income (Expense) Loss before income taxes Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest Income tax benefit Income Tax Expense (Benefit) Net loss Net Income (Loss) Attributable to Parent Net loss per share: Earnings Per Share, Basic and Diluted [Abstract] Basic and diluted loss per share (in dollars per share) Earnings Per Share, Basic and Diluted Weighted average common shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Basic and Diluted Other comprehensive income, net of tax: Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Net unrealized gains in accumulated other comprehensive loss, net of tax expense of $0 and $1,431 for the quarters ended March 31, 2016 and March 31, 2015, respectively Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax Reclassification adjustment for losses (gains) included in net loss, net of tax expense of $0 for the quarters ended March 31, 2016 and 2015 Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax Other comprehensive income, net of tax Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Attributable to Parent Fair Value of Financial Instruments Fair Value Disclosures [Text Block] Warrants Line of Credit and Related Warrants [Text Block] Line of Credit and Related Warrants [Text Block] Net unrealized investment gains in AOCI, tax amount Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax Reclassification adjustment for losses (gains) included in net loss, tax amount Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax Statement of Stockholders' Equity [Abstract] Change in unrealized investment gains/losses, tax Liability for Claims and Claims Adjustment Expense [Table] Liability for Claims and Claims Adjustment Expense [Table] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] Fannie Mae Fannie Mae [Member] Fannie Mae [Member] Liability for Claims and Claims Adjustment Expense [Line Items] Liability for Claims and Claims Adjustment Expense [Line Items] IBNR, default period (at least) Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Default Period Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Default Period Liability for insurance claims Liability for Claims and Claims Adjustment Expense Primary loans in default Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Number of Primary Loans in Default Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Number of Primary Loans in Default Number of loans in pool past due 60 days or more Loans In Pool, Past Due 60 Days Or More, Number Of Loans Loans In Pool, Past Due 60 Days Or More, Number Of Loans Risk in Force of loans in pool past due 60 days or more Loans In Pool, Past Due 60 Days Or More, Loan Risk in Force Loans In Pool, Past Due 60 Days Or More, Risk in Force Deductible on policy Mortgage Pool Insurance, Claim Deductible Mortgage Pool Insurance, Claim Deductible Loan-to-value ratio (less than) Loans In Pool, Loan To Value Ratio Loans In Pool, Loan To Value Ratio Claims applied to deductible Liability for Unpaid Claims and Claims Adjustment Expense, Claims Applied to Deductible Liability for Unpaid Claims and Claims Adjustment Expense, Claims Applied to Deductible Favorable prior year development Prior Year Claims and Claims Adjustment Expense Reserve for prior year insurance claims and claim expenses Liability for Prior Year Claims and Claims Adjustment Expense Liability for Prior Year Claims and Claims Adjustment Expense Future Principal Payments [Abstract] Long-term Debt, Fiscal Year Maturity [Abstract] 2016 Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months 2017 Long-term Debt, Maturities, Repayments of Principal in Year Two 2018 Long-term Debt, Maturities, Repayments of Principal in Year Three Total Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Table] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Domain] Major Types of Debt and Equity Securities [Domain] Asset-backed securities Asset-backed Securities [Member] Schedule of Available-for-sale Securities [Line Items] Schedule of Available-for-sale Securities [Line Items] Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract] Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract] Amortized Cost, Due in one year or less Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis Amortized Cost, Due after one through five years Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis Amortized Cost, Due after five through ten years Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Amortized Cost Basis Amortized Cost, Due after ten years Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis Amortized Cost, Total Investments Available-for-sale Securities, Amortized Cost Basis Available-for-sale Securities, Debt Maturities, Single Maturity Date, Fair Value [Abstract] Available-for-sale Securities, Debt Maturities, Single Maturity Date [Abstract] Fair Value, Due in one year or less Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value Fair Value, Due after one through five years Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value Fair Value, Due after five through ten years Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value Fair Value Due after ten years Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value Fair Value, Total Investments Available-for-sale Securities U.S. Treasury securities and obligations of U.S. government agencies US Treasury and Government [Member] Municipal debt securities US States and Political Subdivisions Debt Securities [Member] Corporate debt securities Corporate Debt Securities [Member] Number of securities, less than 12 months Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year Fair value, less than 12 months Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value Unrealized losses, less than 12 months Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Number of securities,12 months or greater Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year Fair value, 12 months or greater Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value Unrealized losses, 12 months or greater Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Number of securities, total Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions Fair value Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value Unrealized Losses Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss Schedule of Fair Values and Gross Unrealized Gains and Losses Available-for-sale Securities [Table Text Block] Schedule of Investments by Maturity Investments Classified by Contractual Maturity Date [Table Text Block] Schedule of Aging Unrealized Losses Schedule of Unrealized Loss on Investments [Table Text Block] Net Realized Investments Gains (Losses) Realized Gain (Loss) on Investments [Table Text Block] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Earnings per Share Earnings Per Share, Policy [Policy Text Block] Deferred Policy Acquisition Costs Deferred Policy Acquisition Costs, Policy [Policy Text Block] Premium Deficiency Reserves Premium Deficiency Reserves Policy [Policy Text Block] Premium Deficiency Reserves Policy [Policy Text Block] Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Reclassifications Reclassification, Policy [Policy Text Block] Bonds Bonds [Member] Short-term investments Short-term Investments [Member] Amortized Cost Gross Unrealized Gains Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax Gross Unrealized (Losses) Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax Fair Value Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Statement of Financial Position [Abstract] Statement [Table] Statement [Table] Statement [Line Items] Statement [Line Items] Fixed maturities, amortized cost Available-for-sale Debt Securities, Amortized Cost Basis Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares issued (in shares) Common Stock, Shares, Issued Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Common stock, shares authorized (in shares) Common Stock, Shares Authorized Statutory Accounting Practices [Table] Statutory Accounting Practices [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Combined NMic and Re one Combined [Member] NMic and Re one Combined [Member] Statutory Accounting Practices [Line Items] Statutory Accounting Practices [Line Items] Statutory net loss Statutory Accounting Practices, Statutory Net Income Amount Statutory surplus Statutory Accounting Practices, Statutory Capital and Surplus, Balance Contingency reserve Statutory Accounting Practices, Contingency Reserve Contingency reserve recorded under Statutory Accounting Principles is a liability to protect against loss during periods of extreme contraction. Risk-to-Capital Risk To Capital Ratio Regulatory Actual This concept represents an entity's ratio of net risk in force (excludes risk ceded through reinsurance contracts and risk in force on defaulted loans) to the amount of statutory capital (defined as the sum of statutory policyholders' surplus plus statutory contingency reserves). Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] Balance, January 1 Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract] Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract] Current year Current Year Claims and Claims Adjustment Expense Prior years Total claims incurred Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract] Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract] Current year Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year Prior years Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years Total claims paid Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid Balance, March 31 Statement of Cash Flows [Abstract] Cash flows from operating activities Net Cash Provided by (Used in) Operating Activities [Abstract] Net loss Adjustments to reconcile net loss to net cash used in operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Net realized investment losses (gains) Gain from change in fair value of warrant liability Fair Value Adjustment of Warrants Depreciation and other amortization Depreciation, Amortization and Accretion, Net Amortization of debt discount and debt issuance costs Amortization of Financing Costs and Discounts Share-based compensation expense Share-based Compensation Noncash intraperiod tax allocation Expense (Benefit) for Taxes on Current Year Unrealized Gains Expense (Benefit) for Taxes on Current Year Unrealized Gains Changes in operating assets and liabilities: Increase (Decrease) in Other Operating Assets and Liabilities, Net [Abstract] Accrued investment income Increase (Decrease) in Accrued Investment Income Receivable Premiums receivable Increase (Decrease) in Premiums Receivable Prepaid expenses Increase (Decrease) in Prepaid Expense Deferred policy acquisition costs, net Increase (Decrease) in Deferred Policy Acquisition Costs Other assets Increase (Decrease) in Prepaid Expense and Other Assets Unearned premiums Reserve for insurance claims and claims expenses Increase (Decrease) in Loss and Loss Adjustment Expense Reserve Accounts payable and accrued expenses Increase (Decrease) in Accounts Payable and Accrued Liabilities Net cash provided by (used in) operating activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations Cash flows from investing activities Net Cash Provided by (Used in) Investing Activities [Abstract] Purchase of fixed-maturity investments, available-for-sale Payments to Acquire Available-for-sale Securities, Debt Proceeds from redemptions, maturities and sale of fixed-maturity investments, available-for-sale Proceeds from Sale and Maturity of Available-for-sale Securities Purchase of software and equipment Payments to Acquire Property, Plant, and Equipment Net cash provided by (used in) investing activities Net Cash Provided by (Used in) Investing Activities Cash flows from financing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Issuance of common stock Proceeds from Issuance of Common Stock Taxes paid related to net share settlement of equity awards Payments Related to Tax Withholding for Share-based Compensation Repayments of term loan Repayments of Long-term Debt Net cash used in financing activities Net Cash Provided by (Used in) Financing Activities Net increase (decrease) in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents, beginning of period Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents, end of period Noncash financing activities Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Interest paid Interest Paid Common Stock Additional Paid-in Capital Additional Paid-in Capital [Member] Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Income (Loss) [Member] Accumulated Deficit Retained Earnings [Member] Class A Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning balance (in shares) Shares, Outstanding Beginning balance Stockholders' Equity Attributable to Parent Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans Common stock: class A shares issued under stock plans, net of shares withheld for employee taxes Stock Issued During Period, Value, Employee Stock Purchase Plan Share-based compensation expense Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Change in unrealized investment gains/losses, net of tax Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax Net loss Ending balance (in shares) Ending balance Reserves for Insurance Claims and Claim Expenses Liability for Future Policy Benefits and Unpaid Claims Disclosure [Text Block] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Fair Value, Measurements, Recurring Fair Value, Measurements, Recurring [Member] Quoted Prices in Active Markets for Identical Assets (Level 1) Fair Value, Inputs, Level 1 [Member] Significant Other Observable Inputs (Level 2) Fair Value, Inputs, Level 2 [Member] Municipal debt securities Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Available-for-sale securities Cash, cash equivalents and short-term investments Cash and Cash Equivalents, Fair Value Disclosure Total assets Assets, Fair Value Disclosure Warrant liability Warrant Liability Warrant Liability Total liabilities Financial and Nonfinancial Liabilities, Fair Value Disclosure Schedule of Statutory Net Loss, Surplus, Contingency Reserve and Risk-to-Capital Ratio Statutory Accounting Practices Disclosure [Table Text Block] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Sale of Stock [Axis] Sale of Stock [Axis] Sale of Stock [Axis] Sale of Stock [Domain] Sale of Stock [Domain] [Domain] for Sale of Stock [Axis] IPO IPO [Member] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] MAC Financial Holding Corporation and Subsidiaries MAC Financial Holding Corporation and Subsidiaries [Member] MAC Financial Holding Corporation and Subsidiaries [Member] NMI Services, Inc. NMI Services, Inc. [Member] NMI Services, Inc. [Member] Business Acquisition [Line Items] Business Acquisition [Line Items] Stock issued during period, shares, net issues (in shares) Stock Issued During Period, Shares, New Issues Proceeds from issuance of common stock, net of stock issuance costs Proceeds From Issuance of Common Stock, Net of Stock Issuance Costs Proceeds From Issuance of Common Stock, Net of Stock Issuance Costs Consideration transferred, cash and equity interests issued and issuable Business Combination, Consideration Transferred, Cash and Equity Interests Issued and Issuable Business Combination, Consideration Transferred, Cash and Equity Interests Issued and Issuable Consideration transferred, liabilities incurred Business Combination, Consideration Transferred, Liabilities Incurred Number of states in which the entity operates Number of States in which Entity Operates Capitalized wholly owned subsidiary, amount Payment to Investment in Subsidiary Payment to Investment in Subsidiary Antidilutive securities excluded from computation of earnings per share (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Deferred policy acquisition cost, amortization expense Deferred Policy Acquisition Cost, Amortization Expense Premium deficiency reserve Premium Deficiency Reserve, Expense Premium Deficiency Reserve, Expense Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] Fixed Maturities Fixed Maturities [Member] Unrealized loss position, accumulated loss Unrealized losses, 12 months or greater Investment Income, gross Investment Income Gross Investment Income Gross Investment income, investment expense Investment Income, Investment Expense Cash and investments held with various state insurance departments Cash, Cash Equivalents, and Short-term Investments Share Price (in dollars per share) Share Price Risk free rate Fair Value Assumptions, Risk Free Interest Rate Expected term Fair Value Assumptions, Expected Term Volatility assumption Fair Value Assumptions, Expected Volatility Rate Expected dividend rate Fair Value Assumptions, Expected Dividend Rate Assets Assets [Abstract] Fixed maturities, available-for-sale, at fair value (amortized cost of $551,780 and $564,319 as of March 31, 2016 and December 31, 2015, respectively) Available-for-sale Securities, Debt Securities Cash and cash equivalents Premiums receivable Premiums Receivable, Net Accrued investment income Accrued Investment Income Receivable Prepaid expenses Prepaid Expense Deferred policy acquisition costs, net Deferred Policy Acquisition Costs Software and equipment, net Property, Plant and Equipment, Net Intangible assets and goodwill Intangible Assets, Net (Including Goodwill) Other assets Other Assets Total assets Assets Liabilities Liabilities [Abstract] Term loan Long-term Debt Unearned premiums Unearned Premiums Accounts payable and accrued expenses Accounts Payable and Accrued Liabilities Reserve for insurance claims and claim expenses Warrant liability, at fair value Deferred tax Deferred Tax Liabilities, Net Total liabilities Liabilities Commitments and contingencies Commitments and Contingencies Shareholders' Equity Stockholders' Equity Attributable to Parent [Abstract] Common stock - class A shares, $0.01 par value; 59,080,468 and 58,807,825 shares issued and outstanding as of March 31, 2016 and December 31, 2015, respectively (250,000,000 shares authorized) Common Stock, Value, Outstanding Additional paid-in capital Additional Paid in Capital Accumulated other comprehensive loss, net of tax Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated deficit Retained Earnings (Accumulated Deficit) Total shareholders' equity Total liabilities and shareholders' equity Liabilities and Equity Operating Loss Carryforwards [Table] Operating Loss Carryforwards [Table] Income Tax Authority [Axis] Income Tax Authority [Axis] Income Tax Authority [Domain] Income Tax Authority [Domain] Domestic Tax Authority Domestic Tax Authority [Member] Income Tax Authority, Name [Axis] Income Tax Authority, Name [Axis] Income Tax Authority, Name [Domain] Income Tax Authority, Name [Domain] Internal Revenue Service (IRS) Internal Revenue Service (IRS) [Member] Operating Loss Carryforwards [Line Items] Operating Loss Carryforwards [Line Items] Federal statutory income tax rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Income taxes paid Income Taxes Paid Operating loss carryforwards Operating Loss Carryforwards Effective income tax rate on pre-tax loss Effective Income Tax Rate Reconciliation, Percent