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Subsequent Events - Additional Information (Detail) (USD $) In Millions, unless otherwise specified | Mar. 31, 2013 | Dec. 31, 2012 | Apr. 03, 2013 Subsequent Events [Member]
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Subsequent Event [Line Items] |  |  |
Principal payments | $ 21.3 | $ 2.0 | $ 2.0

X
- Details
Name: | us-gaap_SubsequentEventLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Redemption Amount Of Principal + References No definition available. + Details
Name: | wmih_RedemptionAmountOfPrincipal
Namespace Prefix: | wmih_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant