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Commitments and Contingencies - Additional Information (Detail) - USD ($)
Dec. 31, 2015
Dec. 31, 2014
Commitments and Contingencies Disclosure [Line Items]    
Accrued guaranty fund $ 6,700,000  
Estimated future of premium tax deductions 11,100,000  
Amount of deposit with governmental authorities required by law 8,400,000 $ 8,900,000
Derivative cash collateral received 800,000 $ 6,400,000
Mortgage Backed Securities    
Commitments and Contingencies Disclosure [Line Items]    
Funds pledged on mortgage loans held investment portfolio $ 18,400,000