Assets and Liabilities of Consolidated Variable Interest Entities (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012
Investments in mortgages and loans, at amortized cost:
Commercial mortgages, mezzanine loans, other loans and preferred equity interests	$ 1,369,782		$ 1,122,377
Allowance for losses	(15,662)	(15,336)	(22,955)	(23,317)	(24,222)	(30,400)
Total investments in mortgages and loans	1,354,120		1,099,422
Investments in real estate, net of accumulated depreciation of $24,290 and 18,538, respectively	1,400,715		1,004,186
Investments in securities and security-related receivables, at fair value	568,279		567,302
Cash and cash equivalents	116,767		88,847	116,623		100,041
Restricted cash	133,374		121,589
Accrued interest receivable	54,929		48,324
Deferred financing costs, net of accumulated amortization of $19,993 and $17,107, respectively	25,141		18,932
Intangible assets, net of accumulated amortization of $3,495 and $568, respectively	23,944		21,554
Total assets	3,756,217		3,027,237
Liabilities and Equity
Indebtedness (including $431,142 and $377,235 at fair value, respectively)	2,613,317		2,086,401
Accrued interest payable	34,164		26,936
Accounts payable and accrued expenses	58,579		32,447
Derivative liabilities	81,998		113,331
Deferred taxes, borrowers' escrows and other liabilities	132,200		79,462
Total liabilities	2,920,258		2,338,577
Shareholders' equity:
Accumulated other comprehensive income (loss)	(43,039)		(63,810)
Retained earnings (deficit)	(1,364,168)		(1,257,306)
Total shareholders' equity	604,162		601,563
Noncontrolling interests	155,621		34,127
Total liabilities and equity	3,756,217		3,027,237
Variable Interest Entities
Investments in mortgages and loans, at amortized cost:
Commercial mortgages, mezzanine loans, other loans and preferred equity interests	1,718,528		1,816,507
Allowance for losses	(16,205)		(17,250)
Total investments in mortgages and loans	1,702,323		1,799,257
Investments in real estate, net of accumulated depreciation of $24,290 and 18,538, respectively	443,428		194,648
Investments in securities and security-related receivables, at fair value	566,330		566,577
Cash and cash equivalents	35,051		3,599
Restricted cash	30,898		40,793
Accrued interest receivable	80,240		68,456
Deferred financing costs, net of accumulated amortization of $19,993 and $17,107, respectively	8,857		10,263
Intangible assets, net of accumulated amortization of $3,495 and $568, respectively	1,327		517
Total assets	2,868,454		2,684,110
Liabilities and Equity
Indebtedness (including $431,142 and $377,235 at fair value, respectively)	2,044,328		1,946,536
Accrued interest payable	83,059		73,122
Accounts payable and accrued expenses	10,767		5,771
Derivative liabilities	81,653		113,323
Deferred taxes, borrowers' escrows and other liabilities	8,634		5,805
Total liabilities	2,228,441		2,144,557
Shareholders' equity:
Accumulated other comprehensive income (loss)	(38,912)		(59,684)
RAIT investment	340,609		311,635
Retained earnings (deficit)	188,809		258,270
Total shareholders' equity	490,506		510,221
Noncontrolling interests	149,507		29,332
Total liabilities and equity	$ 2,868,454		$ 2,684,110