Assets and Liabilities of Consolidated Variable Interest Entities (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Investments in commercial mortgage loans, mezzanine loans and preferred equity interests, at amortized cost:
Commercial mortgage loans, mezzanine loans, and preferred equity interests	$ 731,105		$ 1,270,607
Allowance for loan losses	(16,699)	$ (13,732)	(14,883)	$ (23,514)	$ (13,531)	$ (12,354)
Investments in real estate
Investments in real estate	190,849		274,672
Less: Accumulated depreciation and amortization	(13,671)		(28,768)
Total investments in real estate	177,178		245,904
Cash and cash equivalents	72,224		53,380	89,317
Restricted cash	113,091		157,914	$ 193,580
Accrued interest receivable	28,147		29,664
Other assets	17,652		43,871
Intangible assets
Accumulated amortization	(7,649)		(6,831)
Total intangible assets	4,558		5,376
Total assets	1,133,454		1,791,833
Liabilities and Equity
Accrued interest payable	3,406		4,688
Accounts payable and accrued expenses	8,756		9,641
Total liabilities	1,025,295		1,533,703
Shareholders’ equity:
Total shareholders’ equity	108,159		176,155
Noncontrolling Interests			3,632
Total liabilities and equity	1,133,454		1,791,833
VIE
Investments in commercial mortgage loans, mezzanine loans and preferred equity interests, at amortized cost:
Commercial mortgage loans, mezzanine loans, and preferred equity interests	936,034		1,432,452
Total investments in commercial mortgage loans, mezzanine loans and preferred equity interests	936,034		1,432,452
Investments in real estate
Investments in real estate	25,662		25,536
Less: Accumulated depreciation and amortization	(7,454)		(6,902)
Total investments in real estate	18,208		18,634
Cash and cash equivalents	228		375
Restricted cash	16,768		1,315
Accrued interest receivable	37,878		44,101
Other assets	3,957		20,814
Intangible assets
Total assets	1,013,073		1,517,691
Liabilities and Equity
Indebtedness, net	953,540		1,409,215
Accrued interest payable	7,563		8,336
Accounts payable and accrued expenses	3,281		3,297
Deferred taxes, borrowers’ escrows and other liabilities	183		827
Total liabilities	964,567		1,421,675
Shareholders’ equity:
RAIT investment and Retained earnings (deficit)	48,506		95,978
Total shareholders’ equity	48,506		95,977
Noncontrolling Interests			39
Total liabilities and equity	1,013,073		1,517,691
VIE | RAIT Securitizations
Investments in commercial mortgage loans, mezzanine loans and preferred equity interests, at amortized cost:
Commercial mortgage loans, mezzanine loans, and preferred equity interests	936,034		1,082,528
Total investments in commercial mortgage loans, mezzanine loans and preferred equity interests	936,034		1,082,528
Investments in real estate
Restricted cash	16,354		1,068
Accrued interest receivable	37,878		41,639
Other assets	109		16,860
Intangible assets
Total assets	990,375		1,142,095
Liabilities and Equity
Indebtedness, net	933,977		1,034,750
Accrued interest payable	1,947		1,869
Accounts payable and accrued expenses	37		23
Deferred taxes, borrowers’ escrows and other liabilities	2
Total liabilities	935,963		1,036,642
Shareholders’ equity:
RAIT investment and Retained earnings (deficit)	54,412		105,453
Total shareholders’ equity	54,412		105,453
Total liabilities and equity	990,375		1,142,095
VIE | RAIT VIE Properties
Investments in real estate
Investments in real estate	25,662		25,536
Less: Accumulated depreciation and amortization	(7,454)		(6,902)
Total investments in real estate	18,208		18,634
Cash and cash equivalents	228		283
Restricted cash	414		237
Other assets	3,848		3,954
Intangible assets
Total assets	22,698		23,108
Liabilities and Equity
Indebtedness, net	19,563		19,630
Accrued interest payable	5,616		5,356
Accounts payable and accrued expenses	3,244		3,274
Deferred taxes, borrowers’ escrows and other liabilities	181		184
Total liabilities	28,604		28,444
Shareholders’ equity:
RAIT investment and Retained earnings (deficit)	(5,906)		(5,336)
Total shareholders’ equity	(5,906)		(5,336)
Total liabilities and equity	$ 22,698		23,108
VIE | RAIT Joint Venture VIE
Investments in commercial mortgage loans, mezzanine loans and preferred equity interests, at amortized cost:
Commercial mortgage loans, mezzanine loans, and preferred equity interests			349,924
Total investments in commercial mortgage loans, mezzanine loans and preferred equity interests			349,924
Investments in real estate
Cash and cash equivalents			92
Restricted cash			10
Accrued interest receivable			2,462
Intangible assets
Total assets			352,488
Liabilities and Equity
Indebtedness, net			354,835
Accrued interest payable			1,111
Deferred taxes, borrowers’ escrows and other liabilities			643
Total liabilities			356,589
Shareholders’ equity:
RAIT investment and Retained earnings (deficit)			(4,140)
Total shareholders’ equity			(4,140)
Noncontrolling Interests			39
Total liabilities and equity			$ 352,488