Organization and Basis of Presentation	9 Months Ended
Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	Organization and Basis of Presentation NMI Holdings, Inc. (NMIH) is a Delaware corporation, incorporated in May 2011, to provide private mortgage guaranty insurance (which we refer to as mortgage insurance or MI) through its wholly owned insurance subsidiaries, National Mortgage Insurance Corporation (NMIC) and National Mortgage Reinsurance Inc One (Re One). Freddie Mac and Fannie Mae each approved NMIC as an eligible mortgage insurer, on January 15, 2013 and January 16, 2013, respectively, which approvals are conditioned upon NMIC maintaining certain conditions, generally through the end of 2015 (GSE Approval). In April 2013, NMIC, our primary insurance subsidiary, wrote our first mortgage insurance policy. NMIC is fully licensed to write mortgage insurance in all 50 states and D.C. In August 2015, NMIH capitalized with $0.5 million a wholly owned subsidiary, NMI Services, Inc., through which we expect to offer outsourced loan review services to mortgage loan originators starting in the fourth quarter of 2015. As of September 30, 2015, we had $10.6 billion of primary insurance in force (IIF) and $4.3 billion of pool IIF, with $2.6 billion of primary risk-in-force (RIF) and $93.1 million of pool RIF. Basis of Presentation The accompanying unaudited condensed consolidated financial statements, which include the results of NMIH and its wholly owned subsidiaries, have been prepared in accordance with the instructions to Form 10-Q as prescribed by the SEC for interim reporting and include other information and disclosures required by accounting principles generally accepted in the U.S. (GAAP). Our accounts are maintained in U.S. dollars. These statements should be read in conjunction with our consolidated financial statements and notes thereto for the year ended December 31, 2014 included in our Annual Report on Form 10-K. All intercompany transactions have been eliminated. The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect reported amounts of assets and liabilities, as well as disclosure of contingent assets and liabilities as of the balance sheet date. Estimates also affect the reported amounts of income and expenses for the reporting period. Actual results could differ from those estimates. The results of operations for the interim period may not be indicative of the results that may be expected for the full year ending December 31, 2015. Earnings per Share 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 share-based compensation arrangements, and the dilutive effect of outstanding warrants. As a result of our net losses for the nine months ended September 30, 2015 and 2014, 6,311,956 and 5,854,306, respectively, of our common stock equivalents we issued under share-based compensation arrangements and warrants were not included in the calculation of diluted net loss per share as of such dates because they were anti-dilutive. Deferred Policy Acquisition Costs Costs directly associated with the successful acquisition of mortgage insurance policies, consisting of certain selling expenses and other policy issuance and underwriting expenses, are initially deferred and reported as deferred policy acquisition costs (DAC). For each book year of business, these costs are amortized to expense in proportion to estimated gross profits over the estimated life of the policies. Total amortization of DAC for the nine months ended September 30, 2015 and 2014 were $1.8 million and $108 thousand, respectively. Premium Deficiency Reserves We consider whether a premium deficiency exists at each fiscal quarter using best estimate assumptions as of the testing date. Per Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) 944, a premium deficiency reserve shall be recognized if the sum of expected claim costs and claim adjustment expenses, expected dividends to policyholders, unamortized acquisition costs, and maintenance costs exceeds related unearned premiums and anticipated investment income. We have determined that no premium deficiency reserves were necessary for the nine months ended September 30, 2015 or 2014. Recent Accounting Pronouncements In May 2014, the FASB issued Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers (Topic 606). This update is intended to provide a consistent approach in recognizing revenue. In accordance with the new standard, recognition of revenue occurs when a customer obtains control of promised goods or services in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In addition, the new standard requires that reporting companies disclose the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. In August 2015, ASU 2015-14 deferred the provisions of ASU 2014-09 to be effective for interim and annual periods beginning after December 15, 2017. The Company is currently evaluating the impact the adoption of this ASU will have on the consolidated financial statements. Reclassifications Certain items in the financial statements as of September 30, 2015 and for the periods ended September 30, 2014 have been reclassified to conform to the current period's presentation. There was no effect on net income or shareholders' equity previously reported.

Organization and Basis of Presentation

NMI Holdings, Inc. (NMIH) is a Delaware corporation, incorporated in May 2011, to provide private mortgage guaranty insurance (which we refer to as mortgage insurance or MI) through its wholly owned insurance subsidiaries, National Mortgage Insurance Corporation (NMIC) and National Mortgage Reinsurance Inc One (Re One). Freddie Mac and Fannie Mae each approved NMIC as an eligible mortgage insurer, on January 15, 2013 and January 16, 2013, respectively, which approvals are conditioned upon NMIC maintaining certain conditions, generally through the end of 2015 (GSE Approval). In April 2013, NMIC, our primary insurance subsidiary, wrote our first mortgage insurance policy. NMIC is fully licensed to write mortgage insurance in all 50 states and D.C. In August 2015, NMIH capitalized with $0.5 million a wholly owned subsidiary, NMI Services, Inc., through which we expect to offer outsourced loan review services to mortgage loan originators starting in the fourth quarter of 2015.

As of September 30, 2015, we had $10.6 billion of primary insurance in force (IIF) and $4.3 billion of pool IIF, with $2.6 billion of primary risk-in-force (RIF) and $93.1 million of pool RIF.

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements, which include the results of NMIH and its wholly owned subsidiaries, have been prepared in accordance with the instructions to Form 10-Q as prescribed by the SEC for interim reporting and include other information and disclosures required by accounting principles generally accepted in the U.S. (GAAP). Our accounts are maintained in U.S. dollars. These statements should be read in conjunction with our consolidated financial statements and notes thereto for the year ended December 31, 2014 included in our Annual Report on Form 10-K. All intercompany transactions have been eliminated. The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect reported amounts of assets and liabilities, as well as disclosure of contingent assets and liabilities as of the balance sheet date. Estimates also affect the reported amounts of income and expenses for the reporting period. Actual results could differ from those estimates. The results of operations for the interim period may not be indicative of the results that may be expected for the full year ending December 31, 2015.

Earnings per Share

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 share-based compensation arrangements, and the dilutive effect of outstanding warrants. As a result of our net losses for the nine months ended September 30, 2015 and 2014, 6,311,956 and 5,854,306, respectively, of our common stock equivalents we issued under share-based compensation arrangements and warrants were not included in the calculation of diluted net loss per share as of such dates because they were anti-dilutive.

Deferred Policy Acquisition Costs

Costs directly associated with the successful acquisition of mortgage insurance policies, consisting of certain selling expenses and other policy issuance and underwriting expenses, are initially deferred and reported as deferred policy acquisition costs (DAC). For each book year of business, these costs are amortized to expense in proportion to estimated gross profits over the estimated life of the policies. Total amortization of DAC for the nine months ended September 30, 2015 and 2014 were $1.8 million and $108 thousand, respectively.

Premium Deficiency Reserves

We consider whether a premium deficiency exists at each fiscal quarter using best estimate assumptions as of the testing date. Per Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) 944, a premium deficiency reserve shall be recognized if the sum of expected claim costs and claim adjustment expenses, expected dividends to policyholders, unamortized acquisition costs, and maintenance costs exceeds related unearned premiums and anticipated investment income. We have determined that no premium deficiency reserves were necessary for the nine months ended September 30, 2015 or 2014.

Recent Accounting Pronouncements

In May 2014, the FASB issued Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers (Topic 606). This update is intended to provide a consistent approach in recognizing revenue. In accordance with the new standard, recognition of revenue occurs when a customer obtains control of promised goods or services in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In addition, the new standard requires that reporting companies disclose the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. In August 2015, ASU 2015-14 deferred the provisions of ASU 2014-09 to be effective for interim and annual periods beginning after December 15, 2017. The Company is currently evaluating the impact the adoption of this ASU will have on the consolidated financial statements.

Reclassifications

Certain items in the financial statements as of September 30, 2015 and for the periods ended September 30, 2014 have been reclassified to conform to the current period's presentation. There was no effect on net income or shareholders' equity previously reported.