CRE Debt and Preferred Equity Investments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013
Transaction to Real Estate Investments [Line Items]
Net investment in CRE Debt and Preferred Equity Investments	$ 1,583,969
Carrying Value	1,588,859
Commercial Mortgage
Transaction to Real Estate Investments [Line Items]
Net origination fees	(4,890)
Outstanding Principal	1,587,223
Carrying Value	1,588,859
Percentage of Loan Portfolio	100.00%	[1]
Commercial Mortgage | Senior Mortgages
Transaction to Real Estate Investments [Line Items]
Outstanding Principal	669,512
Carrying Value	669,949
Percentage of Loan Portfolio	42.20%	[1]
Commercial Mortgage | Subordinated Notes
Transaction to Real Estate Investments [Line Items]
Outstanding Principal	41,059
Carrying Value	41,408
Percentage of Loan Portfolio	2.60%	[1]
Commercial Mortgage | Mezzanine Loans
Transaction to Real Estate Investments [Line Items]
Outstanding Principal	626,883
Carrying Value	628,357
Percentage of Loan Portfolio	39.50%	[1]
Commercial Mortgage | Preferred Equity Interests
Transaction to Real Estate Investments [Line Items]
Outstanding Principal	249,769
Carrying Value	$ 249,145
Percentage of Loan Portfolio	15.70%	[1]

[1] Based on outstanding principal