Loan Participations Sold - Summary of Statistics for Loan Participations Sold (Detail) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2016 USD ($) Loans	Dec. 31, 2015 USD ($) Loans
Participating Mortgage Loans [Line Items]
Count | Loans	2	3
Principal Balance	$ 495,912	$ 608,554
Book Value	$ 409,654	$ 497,032
Weighted Average Term	2019-09	2018-11
Senior Participation [Member]
Participating Mortgage Loans [Line Items]
Count | Loans	2	3
Principal Balance	$ 411,427	$ 498,992
Book Value	409,654	497,032
Guarantee	$ 31,123	$ 35,558
Weighted Average Term	2019-09	2018-11
LIBOR [Member]
Participating Mortgage Loans [Line Items]
Weighted Average Yield/Cost	4.51%	4.15%
LIBOR [Member] | Senior Participation [Member]
Participating Mortgage Loans [Line Items]
Weighted Average Yield/Cost	2.71%	2.49%