The Company and its Subsidiaries	3 Months Ended
Mar. 31, 2018
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 since May 11, 2015. WMIH 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”). Additionally, WMIH is the direct parent of Wand Merger Corporation, a Delaware corporation (“Merger Sub”). Since emerging from bankruptcy on March 19, 2012 (the “Effective Date”), we have had limited operations other than WMMRC’s legacy reinsurance business, which is being operated in runoff mode. Since the Effective Date, our primary strategic objective has been to identify and consummate one or more acquisitions of an operating business, either through a merger, purchase, business combination or other form of acquisition. To that end, we have continued to seek, identify and evaluate acquisition opportunities of varying sizes across an array of industries for the purpose of facilitating an acquisition by WMIH of one or more operating businesses. Since 2014, in addition to management’s ongoing efforts, WMIH has worked with our strategic partner, an affiliate of KKR & CO. L.P. (together with its affiliates, “KKR”), to identify and evaluate potential acquisition opportunities. On February 12, 2018, WMIH, Merger Sub and Nationstar Mortgage Holdings Inc., a Delaware corporation that is currently listed on the New York Stock Exchange under the ticker symbol “NSM” (“Nationstar”), entered into an Agreement and Plan of Merger (the “Merger Agreement”), pursuant to which, subject to the satisfaction or waiver of the conditions set forth therein, Merger Sub will merge with and into Nationstar (the “Nationstar Transaction” or the “Merger”), with Nationstar continuing as the surviving corporation and a wholly-owned subsidiary of WMIH. Subject to the terms and conditions of the Merger Agreement, at the effective time of the Merger (the “Merger Effective Time”) and as a result of the Merger, each share of Nationstar’s common stock issued and outstanding immediately prior to the Merger Effective Time (other than shares owned, directly or indirectly, by Nationstar, WMIH or Merger Sub or by any Nationstar stockholder who properly exercises and perfects appraisal of his, her or its shares under Delaware law) will be converted into the right to receive, at the election of the holder of such share, (i) $18.00 per share in cash, without interest, or (ii) 12.7793 shares of validly issued, fully paid and nonassessable shares of WMIH common stock, par value $0.00001 per share, subject in each case to pro rata cutbacks to the extent cash or stock is oversubscribed (the “Merger Consideration”). The aggregate amount of cash to be paid as Merger Consideration in the Merger is approximately $1.2 billion. If we do not consummate the Nationstar Transaction or another Acquisition or Qualified Acquisition (as such terms are defined in our Amended and Restated Certificate of Incorporation (as amended, the “Certificate of Incorporation”)) on or prior to October 5, 2019 (the “Series B Redemption Date”), as such date may be extended in accordance with the provisions of our Certificate of Incorporation, the outstanding shares of WMIH’s 5.00% Series B Convertible Preferred Stock (the “Series B Preferred Stock”) would be required to be redeemed, as more fully described in Note 9: Capital Stock and Derivative Instruments. As of March 31, 2018, 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 March 31, 2018 and December 31, 2017, 206,714,132 shares, respectively, of WMIH’s common stock were issued and outstanding. As of March 31, 2018 and December 31, 2017, 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, 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 Series B Preferred Stock. As of March 31, 2018, 600,000 shares of Series B Preferred Stock were issued and outstanding. WMMRC WMMRC is a wholly-owned subsidiary of WMIH. Prior to August 2008 (at which time WMMRC became a direct subsidiary of Washington Mutual, Inc. (“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. In addition, the RMIC reinsurance agreement was terminated on February 2, 2018, and the remaining trust assets were distributed to WMMRC per the terms of the agreement. On February 13, 2018, the aggregate excess of loss reinsurance agreement between WMMRC and GMIC was terminated in accordance with the terms of the agreement. The underlying trust and the related quota share agreement remain in place. As a result, WMMRC’s current continuing operations consist solely of the runoff of coverage associated with mortgages placed with the following two remaining carriers, GMIC and MGIC. 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. Merger Sub On February 6, 2018, Merger Sub was formed as a wholly-owned subsidiary of WMIH.

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 since May 11, 2015. WMIH 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”). Additionally, WMIH is the direct parent of Wand Merger Corporation, a Delaware corporation (“Merger Sub”).

Since emerging from bankruptcy on March 19, 2012 (the “Effective Date”), we have had limited operations other than WMMRC’s legacy reinsurance business, which is being operated in runoff mode. Since the Effective Date, our primary strategic objective has been to identify and consummate one or more acquisitions of an operating business, either through a merger, purchase, business combination or other form of acquisition. To that end, we have continued to seek, identify and evaluate acquisition opportunities of varying sizes across an array of industries for the purpose of facilitating an acquisition by WMIH of one or more operating businesses. Since 2014, in addition to management’s ongoing efforts, WMIH has worked with our strategic partner, an affiliate of KKR & CO. L.P. (together with its affiliates, “KKR”), to identify and evaluate potential acquisition opportunities.

On February 12, 2018, WMIH, Merger Sub and Nationstar Mortgage Holdings Inc., a Delaware corporation that is currently listed on the New York Stock Exchange under the ticker symbol “NSM” (“Nationstar”), entered into an Agreement and Plan of Merger (the “Merger Agreement”), pursuant to which, subject to the satisfaction or waiver of the conditions set forth therein, Merger Sub will merge with and into Nationstar (the “Nationstar Transaction” or the “Merger”), with Nationstar continuing as the surviving corporation and a wholly-owned subsidiary of WMIH. Subject to the terms and conditions of the Merger Agreement, at the effective time of the Merger (the “Merger Effective Time”) and as a result of the Merger, each share of Nationstar’s common stock issued and outstanding immediately prior to the Merger Effective Time (other than shares owned, directly or indirectly, by Nationstar, WMIH or Merger Sub or by any Nationstar stockholder who properly exercises and perfects appraisal of his, her or its shares under Delaware law) will be converted into the right to receive, at the election of the holder of such share, (i) $18.00 per share in cash, without interest, or (ii) 12.7793 shares of validly issued, fully paid and nonassessable shares of WMIH common stock, par value $0.00001 per share, subject in each case to pro rata cutbacks to the extent cash or stock is oversubscribed (the “Merger Consideration”). The aggregate amount of cash to be paid as Merger Consideration in the Merger is approximately $1.2 billion.

If we do not consummate the Nationstar Transaction or another Acquisition or Qualified Acquisition (as such terms are defined in our Amended and Restated Certificate of Incorporation (as amended, the “Certificate of Incorporation”)) on or prior to October 5, 2019 (the “Series B Redemption Date”), as such date may be extended in accordance with the provisions of our Certificate of Incorporation, the outstanding shares of WMIH’s 5.00% Series B Convertible Preferred Stock (the “Series B Preferred Stock”) would be required to be redeemed, as more fully described in Note 9: Capital Stock and Derivative Instruments.

As of March 31, 2018, 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 March 31, 2018 and December 31, 2017, 206,714,132 shares, respectively, of WMIH’s common stock were issued and outstanding. As of March 31, 2018 and December 31, 2017, 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, 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 Series B Preferred Stock. As of March 31, 2018, 600,000 shares of Series B Preferred Stock were issued and outstanding.

WMMRC

WMMRC is a wholly-owned subsidiary of WMIH. Prior to August 2008 (at which time WMMRC became a direct subsidiary of Washington Mutual, Inc. (“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. In addition, the RMIC reinsurance agreement was terminated on February 2, 2018, and the remaining trust assets were distributed to WMMRC per the terms of the agreement. On February 13, 2018, the aggregate excess of loss reinsurance agreement between WMMRC and GMIC was terminated in accordance with the terms of the agreement. The underlying trust and the related quota share agreement remain in place. As a result, WMMRC’s current continuing operations consist solely of the runoff of coverage associated with mortgages placed with the following two remaining carriers, GMIC and MGIC.

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.

Merger Sub

On February 6, 2018, Merger Sub was formed as a wholly-owned subsidiary of WMIH.