Secured Debt Agreements - Summary of Statistics for Asset-Specific Financings (Detail) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016 USD ($) Loans	Dec. 31, 2015 USD ($) Loans
Collateral Assets [Member]
Participating Mortgage Loans [Line Items]
Number of loans | Loans	4	2
Principal balance	$ 214,941	$ 154,192
Book value	$ 211,292	$ 153,542
Collateral Assets [Member] | Weighted-Average Cash Coupon [Member] | LIBOR [Member]
Participating Mortgage Loans [Line Items]
Weighted-average cash coupon, Basis spread on variable rate	5.22%	5.27%
Collateral Assets [Member] | Weighted-Average All-in Cost of Credit [Member] | LIBOR [Member]
Participating Mortgage Loans [Line Items]
Weighted-average cost / all-in yield, rate	5.84%	5.83%
Asset-Specific Financings [Member]
Participating Mortgage Loans [Line Items]
Number of loans | Loans	4	2
Principal balance	$ 157,034	$ 111,746
Book value	$ 154,751	$ 111,061
Asset-Specific Financings [Member] | Weighted-Average Cash Coupon [Member] | LIBOR [Member]
Participating Mortgage Loans [Line Items]
Weighted-average cash coupon, Basis spread on variable rate	2.70%	2.52%
Asset-Specific Financings [Member] | Weighted-Average All-in Cost of Credit [Member] | LIBOR [Member]
Participating Mortgage Loans [Line Items]
Weighted-average cost / all-in yield, rate	3.12%	2.88%