Fair Value Measurements - Unobservable Inputs Assumptions - Securitized Debt (Detail) - Fair Value, Inputs, Level 3 [Member] - Securitized Debt at Fair Value, Collateralized by Loans Held for Investment [Member]	Dec. 31, 2015	Dec. 31, 2014
Minimum [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Significant unobservable input, prepayment rate	4.00%	3.00%
Significant unobservable input, default rate	0.00%	0.00%
Significant unobservable input, loss severity rate	35.00%	50.00%
Maximum [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Significant unobservable input, prepayment rate	32.00%	8.00%
Significant unobservable input, default rate	6.00%	9.00%
Significant unobservable input, loss severity rate	65.00%	73.00%