The Company and its Subsidiaries	12 Months Ended
Dec. 31, 2017
Accounting Policies [Abstract]
The Company and its Subsidiaries	Note 1: The Company and its Subsidiaries WMIH Corp. WMIH Corp. (“WMIH”) is a corporation duly organized and existing under the laws of the State of Delaware. On May 11, 2015, WMIH merged with its parent corporation, WMI Holdings Corp., a Washington corporation (“WMIHC”), with WMIH as the surviving corporation in the merger. This transaction occurred as part of the reincorporation of WMIHC from the State of Washington to the State of Delaware effective May 11, 2015 (the “Reincorporation Date”). WMIH, formerly known as WMIHC and Washington Mutual, Inc. (“WMI”), is the direct parent of WM Mortgage Reinsurance Company, Inc., a Hawaii corporation (“WMMRC”), and, until its dissolution on January 18, 2018, WMI Investment Corp., a Delaware corporation (“WMIIC”). Since emergence from bankruptcy on March 19, 2012, our business activities consist of operating WMMRC’s legacy reinsurance business in runoff mode. In addition, we are actively seeking acquisition opportunities across a broad array of industries with a specific focus in the financial services industry, including targets with consumer finance, specialty finance, leasing or insurance operations. As of December 31, 2017, WMIH was authorized to issue up to 3,500,000,000 shares of common stock, and up to 10,000,000 shares of preferred stock (in one or more series), in each case with a par value of $0.00001 per share. As of December 31, 2017 and December 31, 2016, 206,714,132 and 206,380,800 shares, respectively, of WMIH’s common stock were issued and outstanding. As of December 31, 2017 and December 31, 2016, 1,000,000 shares of WMIH’s Series A Convertible Preferred Stock (the “Series A Preferred Stock”) were issued and outstanding. As of December 31, 2017 and December 31, 2016, 600,000 shares of WMIH’s 3% Series B Convertible Preferred Stock (the “Original Series B Preferred Stock”) were issued and outstanding. On December 11, 2017, we announced an amendment of the Original Series B Preferred Stock (the “Series B Amendment”), which amendment became automatically effective at 12:00 a.m., New York City time, on January 5, 2018, and effected an exchange of the previously outstanding Original Series B Preferred Stock for shares of WMIH’s 5.00% Series B Convertible Preferred Stock (the “Series B Preferred Stock”). While we remain committed to consummating an acquisition, we also are mindful that the Company’s Series B Preferred Stock is redeemable on October 5, 2019, if we have not consummated a Qualified Acquisition, as more fully described in Note 6: Service Agreements and Related Party Transactions, on or prior to October 5, 2019 (the “Series B Redemption Date”); provided, if prior to the Series B Redemption Date we have publicly announced that WMIH has entered into a definitive agreement for an Acquisition (as defined below), the Series B Redemption Date will be extended to the earlier of April 5, 2020 and the day immediately following the date such definitive agreement is terminated or the date such Acquisition is closed. There can be no assurance that any transaction will occur or if so on what terms. WMMRC WMMRC is a wholly-owned subsidiary of WMIH. Prior to August 2008 (at which time WMMRC became a direct subsidiary of WMI), WMMRC was a wholly-owned subsidiary of FA Out-of-State Holdings, Inc., a second-tier subsidiary of Washington Mutual Bank (“WMB”) and third-tier subsidiary of WMI. WMMRC is a pure captive insurance company domiciled in the State of Hawaii. WMMRC was incorporated on February 25, 2000, and received a Certificate of Authority, dated March 2, 2000, from the Insurance Division of the State of Hawaii. WMMRC was originally organized to reinsure private mortgage insurance risk for seven primary mortgage insurers then offering private mortgage insurance on loans originated or purchased by former subsidiaries of WMI. The seven primary mortgage insurers are United Guaranty Residential Insurance Company (“UGRIC”), Genworth Mortgage Insurance Corporation (“GMIC”), Mortgage Guaranty Insurance Corporation (“MGIC”), PMI Mortgage Insurance Company (“PMI”), Radian Guaranty Incorporated (“Radian”), Republic Mortgage Insurance Company (“RMIC”) and Triad Guaranty Insurance Company (“Triad”). Due to the then deteriorating performance in the mortgage guarantee markets and the closure and receivership of WMB, the reinsurance agreements with each of the primary mortgage insurers were terminated or placed into runoff during 2008. The agreements with UGRIC and Triad were placed into runoff effective May 31, 2008. The agreements with all other primary mortgage insurers were placed into runoff effective September 26, 2008. As a result, effective September 26, 2008, WMMRC’s continuing operations consisted solely of the runoff of coverage associated with mortgages placed with the primary mortgage carriers prior to September 26, 2008. In runoff, an insurer generally writes no new business but continues to service its obligations under in force policies and otherwise continues as a licensed insurer. The reinsurance agreements with Triad, PMI, UGRIC and Radian were commuted on August 31, 2009, October 2, 2012, April 3, 2014 and October 23, 2017, respectively, and the related trust assets were distributed in accordance with the commutation agreements. As a result, WMMRC’s continuing operations as of December 31, 2017 consist solely of the runoff of coverage associated with mortgages placed with three remaining carriers: GMIC, MGIC and RMIC. On February 2, 2018 the reinsurance agreement with RMIC was terminated and the assets of the trust distributed in accordance with the terms of the trust. On February 13, 2018, the aggregate excess of loss reinsurance agreement between WMMRC and GMIC was terminated in accordance with the provisions of the agreement. See Note 15: Subsequent Events. WMIIC WMIIC was dissolved on January 18, 2018. As of December 31, 2017 and the date of its dissolution, WMIIC did not have any operations and was fully eliminated upon consolidation. For more information on the dissolution of WMIIC see Note 15: Subsequent Events.

Note 1: The Company and its Subsidiaries

WMIH Corp.

WMIH Corp. (“WMIH”) is a corporation duly organized and existing under the laws of the State of Delaware. On May 11, 2015, WMIH merged with its parent corporation, WMI Holdings Corp., a Washington corporation (“WMIHC”), with WMIH as the surviving corporation in the merger. This transaction occurred as part of the reincorporation of WMIHC from the State of Washington to the State of Delaware effective May 11, 2015 (the “Reincorporation Date”).

WMIH, formerly known as WMIHC and Washington Mutual, Inc. (“WMI”), is the direct parent of WM Mortgage Reinsurance Company, Inc., a Hawaii corporation (“WMMRC”), and, until its dissolution on January 18, 2018, WMI Investment Corp., a Delaware corporation (“WMIIC”). Since emergence from bankruptcy on March 19, 2012, our business activities consist of operating WMMRC’s legacy reinsurance business in runoff mode. In addition, we are actively seeking acquisition opportunities across a broad array of industries with a specific focus in the financial services industry, including targets with consumer finance, specialty finance, leasing or insurance operations.

As of December 31, 2017, WMIH was authorized to issue up to 3,500,000,000 shares of common stock, and up to 10,000,000 shares of preferred stock (in one or more series), in each case with a par value of $0.00001 per share. As of December 31, 2017 and December 31, 2016, 206,714,132 and 206,380,800 shares, respectively, of WMIH’s common stock were issued and outstanding. As of December 31, 2017 and December 31, 2016, 1,000,000 shares of WMIH’s Series A Convertible Preferred Stock (the “Series A Preferred Stock”) were issued and outstanding. As of December 31, 2017 and December 31, 2016, 600,000 shares of WMIH’s 3% Series B Convertible Preferred Stock (the “Original Series B Preferred Stock”) were issued and outstanding. On December 11, 2017, we announced an amendment of the Original Series B Preferred Stock (the “Series B Amendment”), which amendment became automatically effective at 12:00 a.m., New York City time, on January 5, 2018, and effected an exchange of the previously outstanding Original Series B Preferred Stock for shares of WMIH’s 5.00% Series B Convertible Preferred Stock (the “Series B Preferred Stock”).

While we remain committed to consummating an acquisition, we also are mindful that the Company’s Series B Preferred Stock is redeemable on October 5, 2019, if we have not consummated a Qualified Acquisition, as more fully described in Note 6: Service Agreements and Related Party Transactions, on or prior to October 5, 2019 (the “Series B Redemption Date”); provided, if prior to the Series B Redemption Date we have publicly announced that WMIH has entered into a definitive agreement for an Acquisition (as defined below), the Series B Redemption Date will be extended to the earlier of April 5, 2020 and the day immediately following the date such definitive agreement is terminated or the date such Acquisition is closed. There can be no assurance that any transaction will occur or if so on what terms.

WMMRC

WMMRC is a wholly-owned subsidiary of WMIH. Prior to August 2008 (at which time WMMRC became a direct subsidiary of WMI), WMMRC was a wholly-owned subsidiary of FA Out-of-State Holdings, Inc., a second-tier subsidiary of Washington Mutual Bank (“WMB”) and third-tier subsidiary of WMI. WMMRC is a pure captive insurance company domiciled in the State of Hawaii. WMMRC was incorporated on February 25, 2000, and received a Certificate of Authority, dated March 2, 2000, from the Insurance Division of the State of Hawaii.

WMMRC was originally organized to reinsure private mortgage insurance risk for seven primary mortgage insurers then offering private mortgage insurance on loans originated or purchased by former subsidiaries of WMI. The seven primary mortgage insurers are United Guaranty Residential Insurance Company (“UGRIC”), Genworth Mortgage Insurance Corporation (“GMIC”), Mortgage Guaranty Insurance Corporation (“MGIC”), PMI Mortgage Insurance Company (“PMI”), Radian Guaranty Incorporated (“Radian”), Republic Mortgage Insurance Company (“RMIC”) and Triad Guaranty Insurance Company (“Triad”).

Due to the then deteriorating performance in the mortgage guarantee markets and the closure and receivership of WMB, the reinsurance agreements with each of the primary mortgage insurers were terminated or placed into runoff during 2008. The agreements with UGRIC and Triad were placed into runoff effective May 31, 2008. The agreements with all other primary mortgage insurers were placed into runoff effective September 26, 2008. As a result, effective September 26, 2008, WMMRC’s continuing operations consisted solely of the runoff of coverage associated with mortgages placed with the primary mortgage carriers prior to September 26, 2008. In runoff, an insurer generally writes no new business but continues to service its obligations under in force policies and otherwise continues as a licensed insurer. The reinsurance agreements with Triad, PMI, UGRIC and Radian were commuted on August 31, 2009, October 2, 2012, April 3, 2014 and October 23, 2017, respectively, and the related trust assets were distributed in accordance with the commutation agreements. As a result, WMMRC’s continuing operations as of December 31, 2017 consist solely of the runoff of coverage associated with mortgages placed with three remaining carriers: GMIC, MGIC and RMIC. On February 2, 2018 the reinsurance agreement with RMIC was terminated and the assets of the trust distributed in accordance with the terms of the trust. On February 13, 2018, the aggregate excess of loss reinsurance agreement between WMMRC and GMIC was terminated in accordance with the provisions of the agreement. See Note 15: Subsequent Events.

WMIIC

WMIIC was dissolved on January 18, 2018. As of December 31, 2017 and the date of its dissolution, WMIIC did not have any operations and was fully eliminated upon consolidation. For more information on the dissolution of WMIIC see Note 15: Subsequent Events.