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Insurance Activity - Additional Information (Detail) (USD $) | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Mar. 19, 2012 | 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 | $ 46,300,000 wmih_FairMarketValueReserveBalance |  |  |
Loss contract fair market value reserve | 12,549,000 wmih_LossContractFairMarketValueReserve | 46,319,000 wmih_LossContractFairMarketValueReserve |  | 63,100,000 wmih_LossContractFairMarketValueReserve |
Decreased value of fair market reserve | $ 33,800,000 wmih_FairMarketValueReserveDecrease | $ 5,900,000 wmih_FairMarketValueReserveDecrease | $ 10,900,000 wmih_FairMarketValueReserveDecrease |  |
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
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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
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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
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Fair market value reserve decrease. + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition First loss layer risk percentage of range maximum. + References No definition available. + Details
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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 Loss contract fair market value reserve. + References No definition available. + Details
Name: | wmih_LossContractFairMarketValueReserve
Namespace Prefix: | wmih_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |