Assets and Liabilities of Deconsolidated Variable Interest Entities (Detail) - USD ($) $ in Thousands		3 Months Ended	6 Months Ended
	Jun. 27, 2018	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Assets
Commercial mortgage loans, mezzanine loans, and preferred equity interests		$ 731,105	$ 731,105	$ 1,270,607
Cash and cash equivalents		72,224	72,224	53,380	$ 89,317
Restricted cash		113,091	113,091	157,914	$ 193,580
Accrued interest receivable		28,147	28,147	29,664
Other assets		17,652	17,652	43,871
Liabilities and Equity
Accrued interest payable		3,406	3,406	4,688
Accounts payable and accrued expenses		8,756	8,756	9,641
Borrowers' escrows		55,842	55,842	117,070
Deferred taxes and other liabilities		22,902	22,902	12,116
Shareholders’ equity:
Noncontrolling interests				3,632
Total liabilities and equity		1,133,454	1,133,454	$ 1,791,833
RAIT Joint Venture VIE
Shareholders’ equity:
Loss on deconsolidation of RAIT Venture VIEs, RAIT FL5 & RAIT FL6		$ (8,177)	$ (8,177)
Variable Interest Entity, Not Primary Beneficiary
Shareholders’ equity:
RAIT IV's net investment in RAIT FL5 & RAIT FL6	$ 62,809
Purchase price for RAIT IV's FL5 Interests & FL6 Interests	54,632
Loss on deconsolidation of RAIT Venture VIEs, RAIT FL5 & RAIT FL6	(8,177)
Variable Interest Entity, Not Primary Beneficiary | RAIT Joint Venture VIE | RAIT FL5 & FL6
Assets
Commercial mortgage loans, mezzanine loans, and preferred equity interests	266,502
Cash and cash equivalents	189
Restricted cash	22,569
Accrued interest receivable	1,191
Other assets	1,233
Total assets	291,684
Liabilities and Equity
Indebtedness, net	205,137
Accrued interest payable	502
Accounts payable and accrued expenses	45
Borrowers' escrows	22,549
Deferred taxes and other liabilities	531
Total liabilities	228,764
Shareholders’ equity:
Noncontrolling interests	111
Total liabilities and equity	$ 228,875