Summary of Significant Accounting Policies - Additional Information (Detail)				3 Months Ended		6 Months Ended		12 Months Ended
		Aug. 13, 2018	Jun. 05, 2018 USD ($)	Jun. 30, 2018 USD ($) Loan Instrument shares	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) Loan Instrument shares	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) Loan LandParcel	Jan. 01, 2018 USD ($)
Significant Accounting Policies [Line Items]
Unpaid Principal Balance				$ 958,182,000		$ 958,182,000		$ 1,419,653,000
Preferred dividends declared				$ 0		$ 6,397,000
Cumulative redeemable preferred shares, shares outstanding | shares				0		0
Federal deposit insurance corporation, insurance limit per institution				$ 250,000		$ 250,000
Restricted cash				113,091,000	$ 193,580,000	113,091,000	$ 193,580,000	157,914,000
Accrued interest receivable				28,147,000		28,147,000		29,664,000
Earned asset management fees from consolidated securitizations, eliminated				152,000	215,000	314,000	488,000
Intangible assets, accumulated amortization				7,649,000		7,649,000		6,831,000
Intangible assets, amortization expenses				391,000	1,913,000	818,000	4,560,000
Expected amortization expense of intangible assets, remainder of 2018				757,000		757,000
Expected amortization expense of intangible assets in 2019				1,183,000		1,183,000
Expected amortization expense of intangible assets in 2020				902,000		902,000
Expected amortization expense of intangible assets in 2021				614,000		614,000
Expected amortization expense of intangible assets in 2022				428,000		428,000
Expected amortization expense of intangible assets thereafter				$ 674,000		$ 674,000
Number of derivative instruments outstanding | Instrument				0		0
Reversal of accrued current income tax liability					$ 249,000		$ 249,000
Cumulative effect adjustment as an increase to shareholders’ equity								$ 180,548,000
Number of land parcels sold | LandParcel								2
Revenue from Contracts with Customers | Difference between Revenue Guidance in Effect before and after Topic 606
Significant Accounting Policies [Line Items]
Cumulative effect adjustment as an increase to shareholders’ equity									$ 761,000
Financial Instruments
Significant Accounting Policies [Line Items]
Cumulative effect adjustment increase to accumulated other comprehensive income (loss) and decrease to retained earnings (deficit)									$ 9,257,000
In-place leases
Significant Accounting Policies [Line Items]
Intangible assets, gross carrying amount				$ 12,207,000		$ 12,207,000		$ 12,207,000
Loans and Finance Receivables
Significant Accounting Policies [Line Items]
Accrued interest receivable				$ 24,707,000		24,707,000		23,801,000
Impairment of loans						$ 28,882,000		28,904,000
Number of impaired loans | Loan				4		4
Loans and Finance Receivables | Troubled Debt Restructured Loans
Significant Accounting Policies [Line Items]
Impairment of loans						$ 28,317,000		$ 30,379,000
Number of impaired loans | Loan				3		3		2
Tenant escrows and borrowers' funds
Significant Accounting Policies [Line Items]
Restricted cash				$ 59,338,000		$ 59,338,000		$ 123,398,000
Securitizations
Significant Accounting Policies [Line Items]
Restricted cash				36,508,000		36,508,000		34,516,000
RAIT FL6
Significant Accounting Policies [Line Items]
Restricted cash				17,245,000		$ 17,245,000
Scenario, Forecast
Significant Accounting Policies [Line Items]
Reverse stock split, conversion ratio		0.02
Minimum
Significant Accounting Policies [Line Items]
Average market capitalization required for compliance over a 30-day trading period			$ 15,000,000
Minimum | Building and Building Improvements
Significant Accounting Policies [Line Items]
Property, useful lives						30 years
Minimum | Furniture, fixtures, and equipment
Significant Accounting Policies [Line Items]
Property, useful lives						5 years
Maximum | Building and Building Improvements
Significant Accounting Policies [Line Items]
Property, useful lives						40 years
Maximum | Furniture, fixtures, and equipment
Significant Accounting Policies [Line Items]
Property, useful lives						10 years
Recourse Indebtedness
Significant Accounting Policies [Line Items]
Unpaid Principal Balance				$ 247,096,000		$ 247,096,000		$ 313,700,000
Recourse Indebtedness | 4.0% convertible senior notes
Significant Accounting Policies [Line Items]
Stated interest rate				4.00%		4.00%		4.00%
Unpaid Principal Balance	[1]			$ 68,222,000		$ 68,222,000		$ 110,513,000
Contractual Maturity, month and year	[1]					2033-10		2033-10
Recourse Indebtedness | Senior Secured Notes
Significant Accounting Policies [Line Items]
Unpaid Principal Balance				$ 9,500,000		$ 9,500,000		$ 11,500,000
Contractual Maturity, month and year						2019-04		2019-04
Recourse Indebtedness | 7.125% senior notes
Significant Accounting Policies [Line Items]
Stated interest rate				7.125%		7.125%
Unpaid Principal Balance				$ 68,408,000		$ 68,408,000
Contractual Maturity, month and year						2019-08

[1] Our 4.0% convertible senior notes are redeemable at par, at the option of the holder, in October 2018, October 2023, and October 2028.