Securitized Loans Held for Investment - Roll-Forward (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Securitized Loans Held for Investment at Fair Value [Member]
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Sales and Settlements		$ (9,638)
Transfer due to deconsolidation		(287,806)
Variable Interest Entities, Primary Beneficiary, Aggregated Disclosure [Member] | Securitized Loans Held for Investment at Cost [Member]
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Balance, beginning of period		626,112	$ 783,484
Principal paydowns			(153,063)
Net periodic (amortization) accretion			(4,541)
Change to loan loss provision			232
Balance, end of period			626,112
Variable Interest Entities, Primary Beneficiary, Aggregated Disclosure [Member] | Securitized Loans Held for Investment at Fair Value [Member]
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Balance, beginning of period	[1]	5,306,501
Purchases		577,036	4,722,824
Principal paydowns		(707,996)	(173,597)
Sales and Settlements		(9,638)
Net periodic (amortization) accretion		(19,100)	5,028
Change in fair value		(90,581)	144,960
Transfer due to deconsolidation		(287,806)
Balance, end of period		4,768,416	5,306,501	[1]
Variable Interest Entities, Primary Beneficiary, Aggregated Disclosure [Member] | Securitized Loans Held for Investment at Fair Value [Member] | Previously Reported [Member]
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Balance, beginning of period		$ 4,699,215
Balance, end of period			$ 4,699,215

[1] Includes Securitized loans held for investment of $607 million for which the fair value option election was made beginning January 1, 2015.