v3.7.0.1
Mortgage Loans - Change in Allowance for Credit Losses in Mortgage Loans (Detail)
$ in Thousands
 3 Months Ended
Mar. 31, 2017
USD ($)
Loans
Financing Receivable, Allowance for Credit Losses [Roll Forward]  
Allowance for Credit Losses, Collectively Evaluated for Impairment, Number of Loans, Beginning Balance | Loans 430
Allowance for Credit Losses, Collectively Evaluated for Impairment, Number of Loans, Change in recorded investment | Loans (1)
Allowance for Credit Losses, Collectively Evaluated for Impairment, Number of Loans, Ending Balance | Loans 429
Allowance for Credit Losses, Collectively Evaluated for Impairment, Recorded Investment, Beginning Balance $ 4,358,596
Allowance for Credit Losses, Collectively Evaluated for Impairment, Recorded Investment, Change in recorded investment 100,376
Allowance for Credit Losses, Collectively Evaluated for Impairment, Recorded Investment, Ending Balance 4,458,972
Allowance for Credit Losses, Collectively Evaluated for Impairment, Valuation Allowance, Beginning Balance 11,488
Allowance for Credit Losses, Collectively Evaluated for Impairment, Valuation Allowance, Change in allowance 302
Allowance for Credit Losses, Collectively Evaluated for Impairment, Valuation Allowance,, Ending Balance $ 11,790
Allowance for Credit Losses, Individually Impaired, Number of Loans, Beginning Balance | Loans 2
Allowance for Credit Losses, Individually Impaired, Number of Loans, Change in recorded investment | Loans 1
Allowance for Credit Losses, Individually Impaired, Number of Loans, Ending Balance | Loans 3
Allowance for Credit Losses, Individually Impaired, Recorded Investment, Beginning Balance $ 1,940
Allowance for Credit Losses, Individually Impaired, Recorded Investment, Change in recorded investment 2,285
Allowance for Credit Losses, Individually Impaired, Recorded Investment, Ending Balance 4,225
Allowance for Credit Losses, Individually Impaired, Valuation Allowance, Beginning Balance 1,002
Allowance for Credit Losses, Individually Impaired, Valuation Allowance, Change in allowance 1,324
Allowance for Credit Losses, Individually Impaired, Valuation Allowance, Ending Balance $ 2,326
Allowance for Credit Losses, Number of Loans, Beginning Balance | Loans 432
Allowance for Credit Losses, Number of Loans, Change in recorded investment | Loans 0
Allowance for Credit Losses, Number of Loans, Ending Balance | Loans 432
Allowance for Credit Losses, Recorded Investment, Beginning Balance $ 4,360,536
Allowance for Credit Losses, Recorded Investment, Change in recorded investment 102,661
Allowance for Credit Losses, Recorded Investment, Ending Balance 4,463,197
Allowance for Credit Losses, Valuation Allowance, Beginning Balance 12,490
Allowance for Credit Losses, Valuation Allowance, Change in allowance 1,626
Allowance for Credit Losses, Valuation Allowance, Ending Balance $ 14,116