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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 $ 12,500,000wmih_FairMarketValueReserveBalance   $ 12,500,000wmih_FairMarketValueReserveBalance  
Decrease in expense $ 0wmih_FairMarketValueReserveExpensesDecrease $ 0wmih_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