CRE Debt and Preferred Equity Investments (Detail) - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015
Real Estate [Line Items]
Carrying Value	[1]	$ 1,084,931	$ 1,348,817
Preferred Equity Interests
Real Estate [Line Items]
Carrying Value	[1]	8,967	121,773
Commercial Mortgage
Real Estate [Line Items]
Outstanding Principal	[1]	975,015	1,355,422
Carrying Value	[1],[2]	$ 970,505	$ 1,348,817
Percentage of Loan Portfolio	[1],[3]	100.00%	100.00%
Commercial Mortgage | Mezzanine Loans
Real Estate [Line Items]
Outstanding Principal		$ 453,693	$ 582,592
Carrying Value	[1],[2]	$ 451,467	$ 578,503
Percentage of Loan Portfolio	[3]	46.50%	43.00%
Commercial Mortgage | Senior Mortgages
Real Estate [Line Items]
Outstanding Principal		$ 512,322	$ 387,314
Carrying Value	[1],[2]	$ 510,071	$ 385,838
Percentage of Loan Portfolio	[3]	52.60%	28.60%
Commercial Mortgage | Senior Securitized Mortgages
Real Estate [Line Items]
Outstanding Principal	[4],[5]		$ 263,072
Carrying Value	[1],[2],[4],[5]		$ 262,703
Percentage of Loan Portfolio	[3],[5]	0.00%	19.40%
Commercial Mortgage | Preferred Equity Interests
Real Estate [Line Items]
Outstanding Principal		$ 9,000	$ 122,444
Carrying Value	[2]	$ 8,967	$ 121,773
Percentage of Loan Portfolio	[3]	0.90%	9.00%

[1] Excludes Loans held for sale, net.

[2] Carrying value includes unamortized origination fees of $4.5 million and $6.9 million as of December 31, 2016 and 2015, respectively.

[3] Based on outstanding principal.

[4] Assets of consolidated VIE.

[5] Assets of consolidated VIEs.