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Insurance Activity - Additional Information (Detail) (USD $) | 3 Months Ended |  |
--- | --- | --- | ---
Mar. 31, 2015 | Mar. 31, 2014 | Dec. 31, 2014 | Aug. 31, 2009
Effects of Reinsurance [Line Items] |  |  |  |
Quoted percentage to share base |  |  |  | 50.00%wmih_QuotedPercentageToShareBase
Balances in the fair market reserve | $ 12,500,000 wmih_FairMarketValueReserveBalance |  | $ 12,500,000 wmih_FairMarketValueReserveBalance |
Decrease in expense | $ 0 wmih_FairMarketValueReserveExpensesDecrease | $ 0 wmih_FairMarketValueReserveExpensesDecrease |  |
WMMRC [Member] |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Second loss layer risk percentage of range minimum |  |  |  | 5.00%wmih_SecondLossLayerRiskPercentageOfRangeMinimum / dei_LegalEntityAxis = wmih_WmmrcMember
Second loss layer risk percentage of range maximum |  |  |  | 10.00%wmih_SecondLossLayerRiskPercentageOfRangeMaximum / dei_LegalEntityAxis = wmih_WmmrcMember
First loss layer risk percentage of range minimum |  |  |  | 4.00%wmih_FirstLossLayerRiskPercentageOfRangeMinimum / dei_LegalEntityAxis = wmih_WmmrcMember
First loss layer risk percentage of range maximum |  |  |  | 5.00%wmih_FirstLossLayerRiskPercentageOfRangeMaximum / dei_LegalEntityAxis = wmih_WmmrcMember
Minimum period of reinsurance agreements | 5 years |  |  |
Maximum period of reinsurance agreements | 10 years |  |  |
WMMRC [Member] | Minimum [Member] |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Net of ceding commission, percentage |  |  |  | 25.00%us-gaap_ReinsuranceRecoverablesPercentageOfTotal / dei_LegalEntityAxis = wmih_WmmrcMember / us-gaap_RangeAxis = us-gaap_MinimumMember
WMMRC [Member] | Maximum [Member] |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Net of ceding commission, percentage |  |  |  | 40.00%us-gaap_ReinsuranceRecoverablesPercentageOfTotal / dei_LegalEntityAxis = wmih_WmmrcMember / us-gaap_RangeAxis = us-gaap_MaximumMember

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

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- Definition Percentage of total reinsurance recoverables. + References No definition available. + Details
Name: | us-gaap_ReinsuranceRecoverablesPercentageOfTotal
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition Fair market value reserve balance. + References No definition available. + Details
Name: | wmih_FairMarketValueReserveBalance
Namespace Prefix: | wmih_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Fair market value reserve expenses decrease. + References No definition available. + Details
Name: | wmih_FairMarketValueReserveExpensesDecrease
Namespace Prefix: | wmih_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition First loss layer risk percentage of range maximum. + References No definition available. + Details
Name: | wmih_FirstLossLayerRiskPercentageOfRangeMaximum
Namespace Prefix: | wmih_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition First loss layer risk percentage of range minimum. + References No definition available. + Details
Name: | wmih_FirstLossLayerRiskPercentageOfRangeMinimum
Namespace Prefix: | wmih_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition Maximum period of reinsurance agreements. + References No definition available. + Details
Name: | wmih_MaximumPeriodOfReinsuranceAgreements
Namespace Prefix: | wmih_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Minimum period of reinsurance agreements. + References No definition available. + Details
Name: | wmih_MinimumPeriodOfReinsuranceAgreements
Namespace Prefix: | wmih_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Quoted percentage to share base. + References No definition available. + Details
Name: | wmih_QuotedPercentageToShareBase
Namespace Prefix: | wmih_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition Second loss layer risk percentage of range maximum. + References No definition available. + Details
Name: | wmih_SecondLossLayerRiskPercentageOfRangeMaximum
Namespace Prefix: | wmih_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition Second loss layer risk percentage of range minimum. + References No definition available. + Details
Name: | wmih_SecondLossLayerRiskPercentageOfRangeMinimum
Namespace Prefix: | wmih_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Details
Name: | dei_LegalEntityAxis=wmih_WmmrcMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |