Assets and Liabilities of Consolidated Variable Interest Entities (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011
Investments in mortgages and loans, at amortized cost:
Commercial mortgages, mezzanine loans, other loans and preferred equity interests	$ 1,161,766		$ 1,075,129
Allowance for losses	(24,222)	(26,206)	(30,400)	(39,877)	(39,715)	(46,082)
Total investments in mortgages and loans	1,137,544		1,044,729
Investments in real estate, net of accumulated depreciation of $2,341 and $1,941, respectively	949,649		918,189
Investments in securities and security-related receivables, at fair value	603,173		655,509
Cash and cash equivalents	60,401		100,041	44,265		29,720
Restricted cash	99,119		90,641
Accrued interest receivable	51,331		47,335
Deferred financing costs, net of accumulated amortization of $15,010 and $13,633, respectively	17,863		19,734
Total assets	2,975,575		2,923,980
Liabilities and Equity
Indebtedness (including $304,687 and $187,048 at fair value, respectively)	1,919,620		1,799,595
Accrued interest payable	25,867		24,129
Accounts payable and accrued expenses	26,252		22,990
Derivative liabilities	123,458		151,438
Deferred taxes, borrowers' escrows and other liabilities	52,951		35,704
Total liabilities	2,148,148		2,033,856
Shareholders' equity:
Accumulated other comprehensive income (loss)	(77,527)		(95,173)
Retained earnings	(1,083,924)		(910,086)
Total shareholders' equity	770,523		833,961
Total liabilities and equity	2,975,575		2,923,980
Variable Interest Entities
Investments in mortgages and loans, at amortized cost:
Commercial mortgages, mezzanine loans, other loans and preferred equity interests	1,918,215		1,917,925
Allowance for losses	(17,125)		(17,125)
Total investments in mortgages and loans	1,901,090		1,900,800
Investments in real estate, net of accumulated depreciation of $2,341 and $1,941, respectively	20,317		20,609
Investments in securities and security-related receivables, at fair value	602,555		654,795
Cash and cash equivalents	273		276
Restricted cash	57,270		50,203
Accrued interest receivable	71,082		67,271
Deferred financing costs, net of accumulated amortization of $15,010 and $13,633, respectively	11,364		12,741
Total assets	2,663,951		2,706,695
Liabilities and Equity
Indebtedness (including $304,687 and $187,048 at fair value, respectively)	1,837,445		1,724,356
Accrued interest payable	66,500		59,914
Accounts payable and accrued expenses	3,254		3,335
Derivative liabilities	123,458		151,438
Deferred taxes, borrowers' escrows and other liabilities	5,702		4,877
Total liabilities	2,036,359		1,943,920
Shareholders' equity:
Accumulated other comprehensive income (loss)	(73,309)		(90,954)
RAIT Investment	292,237		295,641
Retained earnings	408,664		558,088
Total shareholders' equity	627,592		762,775
Total liabilities and equity	$ 2,663,951		$ 2,706,695