Internal CRE Debt and Preferred Equity Ratings (Detail) - Commercial Mortgage - USD ($) $ in Thousands		Mar. 31, 2016	Dec. 31, 2015
Transaction to Real Estate Investments [Line Items]
Performing		$ 443,041	$ 520,263
Closely Monitored		419,995	600,561
Special Mention		321,419	234,598
Internal Rating Substandard		0	0
Doubtful		0	0
Loss		0	0
Total	[1]	1,184,455	1,355,422
Senior Mortgages
Transaction to Real Estate Investments [Line Items]
Performing		91,321	71,000
Closely Monitored		243,681	283,148
Special Mention		142,300	33,166
Internal Rating Substandard		0	0
Doubtful		0	0
Loss		0	0
Total		477,302	387,314
Senior Securitized Mortgages
Transaction to Real Estate Investments [Line Items]
Performing	[2]	55,770	106,770
Closely Monitored	[2]	15,500	15,500
Special Mention	[2]	140,802	140,802
Internal Rating Substandard	[2]	0	0
Doubtful	[2]	0	0
Loss	[2]	0	0
Total	[2],[3]	212,072	263,072
Preferred Equity Interests
Transaction to Real Estate Investments [Line Items]
Closely Monitored			81,944
Special Mention		9,000	40,500
Internal Rating Substandard		0	0
Doubtful		0	0
Loss		0	0
Total		9,000	122,444
Mezzanine Loans
Transaction to Real Estate Investments [Line Items]
Performing		295,950	342,493
Closely Monitored		160,814	219,969
Special Mention		29,317	20,130
Internal Rating Substandard		0	0
Doubtful		0	0
Loss		0	0
Total		$ 486,081	$ 582,592

[1] Excludes Loans held for sale.

[2] Assets of consolidated VIE.

[3] Assets of consolidated VIEs.