Fair Values - Schedule of Details of Carrying Amount, Face Amount, and Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Financial liabilities
Loan participations sold	$ 409,654	$ 497,032
Carrying Amount [Member]
Financial assets
Cash and cash equivalents	94,061	96,450
Restricted cash	877	9,556
Loans receivable, net	8,347,712	9,077,007
Financial liabilities
Secured debt agreements	5,320,358	6,116,105
Loan participations sold	409,654	497,032
Convertible notes, net	166,064	164,026
Face Amount [Member]
Financial assets
Cash and cash equivalents	94,061	96,450
Restricted cash	877	9,556
Loans receivable, net	8,381,679	9,108,361
Financial liabilities
Secured debt agreements	5,335,908	6,131,751
Loan participations sold	411,427	498,992
Convertible notes, net	172,500	172,500
Fair Value [Member]
Financial assets
Cash and cash equivalents	94,061	96,450
Restricted cash	877	9,556
Loans receivable, net	8,392,677	9,121,732
Financial liabilities
Secured debt agreements	5,335,908	6,131,751
Loan participations sold	411,427	498,992
Convertible notes, net	$ 190,181	$ 171,344