Equity Investments - Additional Information (Detail) (USD $)	9 Months Ended		12 Months Ended	1 Months Ended	3 Months Ended	9 Months Ended			1 Months Ended	3 Months Ended	9 Months Ended				3 Months Ended		9 Months Ended		1 Months Ended	9 Months Ended		1 Months Ended		3 Months Ended		9 Months Ended		1 Months Ended		3 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Jun. 20, 2013 Atrium Property [Member]	Jun. 30, 2013 Atrium Property [Member]	Sep. 30, 2013 Atrium Property [Member]	May 30, 2013 Sealy [Member]	Sep. 30, 2013 Concord Debt Holdings (1) [Member]	Aug. 31, 2012 10 Metrotech [Member]	Sep. 30, 2013 10 Metrotech [Member]	Sep. 30, 2013 10 Metrotech [Member]	Jul. 30, 2013 10 Metrotech [Member]	Dec. 31, 2012 10 Metrotech [Member]	Sep. 30, 2013 WRT Elad [Member]	Sep. 30, 2013 Vintage Housing Holding LLC [Member]	Sep. 30, 2012 Vintage Housing Holding LLC [Member]	Sep. 30, 2013 Vintage Housing Holding LLC [Member]	Sep. 30, 2012 Vintage Housing Holding LLC [Member]	Feb. 18, 2013 WRT-Elad One South State Equity LP [Member]	Sep. 30, 2013 WRT-Elad One South State Equity LP [Member]	Feb. 25, 2013 Concord Debt Holdings LLC [Member]	Feb. 25, 2013 Lex-Win [Member]	Feb. 25, 2013 CDH CDO LLC [Member]	Sep. 30, 2013 CDH CDO LLC [Member]	Sep. 30, 2012 CDH CDO LLC [Member]	Sep. 30, 2013 CDH CDO LLC [Member]	Sep. 30, 2012 CDH CDO LLC [Member]	Mar. 08, 2013 RE CDO Management LLC [Member]	Feb. 20, 2013 RE CDO Management LLC [Member]	Mar. 31, 2013 RE CDO Management LLC [Member]
Schedule of Equity Method Investments [Line Items]
Increase in occupancy of lease renewal	74.00%		70.00%
Future interest																			5.00%
Future interest																			70.00%
Fee to be paid by the borrower																			$ 1,400,000
Additional increase in indirect future interest																			6.00%
Interests acquired								5,440,000						10,465,000
Nominal % Ownership									33.33%												17.00%
Acquisition Price																						25,000
sales price of the trust																							12,500
Gain on sale of interest																							12,500
Loss on sale of interest																							123,000
Sale of subordinated interests																												6,240,000	2,750,000
Transfer of collateral management agreement																													0
Aggregate amount received from sales																												4,416,000		4,416,000
Loan held by this venture												40,000,000
Acquisition of loan									32,500,000
Discount accretion income	37,000	14,065,000							7,500,000
Equity income Distribution	19,354,000	17,097,000							13,333,000
Equity income recorded									2,676,000
Metrotech's net income										8,028,000	9,853,000				4,563,000	2,160,000	12,708,000	3,550,000						17,914,000	4,814,000	27,182,000	12,748,000
Metrotech's total assets										34,000	34,000		32,535,000
Metrotech's total liabilities										0	0		0
Carrying value of investment	381,939,000		370,436,000				0
Amount of nor-performing mortage loan acquired				10,650,000		10,650,000
Non-performing mortgage loan acquisition cost	21,437,000	64,970,000		6,625,000		6,625,000
Joint venture paid				1,137,000		1,137,000
Investment by trust					$ 3,935,000
Investment lag Period																	1 month			1 month