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Financing Arrangements - Additional Information (Detail) - DebtFinancing | Mar. 31, 2018 | Dec. 31, 2017
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Debt Disclosure [Abstract] |  |
Number of debt financing arrangements in place | 0 | 0

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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Number of debt financing arrangements. + References No definition available. + Details
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Namespace Prefix: | wmih_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant