Investments in Loans (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2014 Loan		Dec. 31, 2013 Loan
Mortgage Loans on Real Estate [Line Items]
Unpaid Principal Balance	$ 1,345,886		$ 1,146,574
Deferred fees	(1,619)		(800)
Total investments in loans, Unpaid Principal Balance	1,344,267		1,145,774
Total investment in loans, Unamortized (Discounts) Premiums	(20,590)		(23,397)
Carrying Amount	1,325,296		1,123,177
Commercial mortgages, mezzanine loans and other loans, Carrying Amount	1,323,677		1,122,377
Number of Loans	176		153
Weighted-Average Coupon	6.70%	[1]	7.20%	[1]
CRE Loans
Mortgage Loans on Real Estate [Line Items]
Unpaid Principal Balance	1,325,748		1,115,949
Total investment in loans, Unamortized (Discounts) Premiums	(20,656)		(23,469)
Carrying Amount	1,305,092		1,092,480
Number of Loans	175		151
Weighted-Average Coupon	6.80%	[1]	7.30%	[1]
Deferred Fee
Mortgage Loans on Real Estate [Line Items]
Total investment in loans, Unamortized (Discounts) Premiums	0		0
Commercial mortgages
Mortgage Loans on Real Estate [Line Items]
Unpaid Principal Balance	1,020,026		792,526
Total investment in loans, Unamortized (Discounts) Premiums	(16,975)		(19,257)
Carrying Amount	1,003,051		773,269
Number of Loans	85		59
Weighted-Average Coupon	6.00%	[1]	6.40%	[1]
Range of Maturity Dates, Minimum	Aug. 01, 2014		Mar. 01, 2014
Range of Maturity Dates, Maximum	Jul. 01, 2044		Jan. 01, 2029
Mezzanine Loans
Mortgage Loans on Real Estate [Line Items]
Unpaid Principal Balance	263,113		269,034
Total investment in loans, Unamortized (Discounts) Premiums	(2,793)		(3,273)
Carrying Amount	260,320		265,761
Number of Loans	80		81
Weighted-Average Coupon	9.50%	[1]	9.60%	[1]
Range of Maturity Dates, Minimum	Sep. 01, 2014		Mar. 01, 2014
Range of Maturity Dates, Maximum	Jan. 01, 2029		Jan. 01, 2029
Preferred Equity Interests
Mortgage Loans on Real Estate [Line Items]
Unpaid Principal Balance	42,609		54,389
Total investment in loans, Unamortized (Discounts) Premiums	(888)		(939)
Carrying Amount	41,721		53,450
Number of Loans	10		11
Weighted-Average Coupon	7.70%	[1]	8.60%	[1]
Range of Maturity Dates, Minimum	May 01, 2015		May 01, 2015
Range of Maturity Dates, Maximum	Aug. 01, 2025		Aug. 01, 2025
Other loans
Mortgage Loans on Real Estate [Line Items]
Unpaid Principal Balance	20,138		30,625
Total investment in loans, Unamortized (Discounts) Premiums	66		72
Carrying Amount, Other loans	$ 20,204		$ 30,697
Number of Loans	1		2
Weighted-Average Coupon	2.80%	[1]	4.30%	[1]
Range of Maturity Dates, Minimum	Oct. 01, 2016		Mar. 01, 2014
Range of Maturity Dates, Maximum			Oct. 01, 2016

[1] Weighted-average coupon is calculated on the unpaid principal amount of the underlying instruments, which does not necessarily correspond to the carrying amount.