Internal CRE Debt and Preferred Equity Ratings (Detail) (Commercial Mortgage, USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Transaction to Real Estate Investments [Line Items]
Performing Loans	$ 1,498,749		$ 1,555,750
Internal Ratings Watch List	9,250
Defaulted-Recovery	12,973		31,473
Workout	0		0
Senior Mortgages
Transaction to Real Estate Investments [Line Items]
Performing Loans	371,331		644,039
Defaulted-Recovery	12,973	[1]	25,473	[1]
Workout	0		0
Subordinated Notes
Transaction to Real Estate Investments [Line Items]
Performing Loans			41,059
Workout	0		0
Mezzanine Loans
Transaction to Real Estate Investments [Line Items]
Performing Loans	522,474		620,883
Defaulted-Recovery			6,000
Workout	0		0
Preferred Equity Interests
Transaction to Real Estate Investments [Line Items]
Performing Loans	214,653		249,769
Workout	0		0
Senior Securitized Mortgages
Transaction to Real Estate Investments [Line Items]
Performing Loans	390,291	[2]
Internal Ratings Watch List	9,250	[2]
Workout	$ 0	[2]

[1] Relates to one loan on nonaccrual status.

[2] Assets of consolidated VIE.