Supplemental Disclosure to Consolidated Statements of Cash Flows - Additional Information (Detail) $ in Thousands						1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 27, 2018 USD ($) shares	Mar. 19, 2018 USD ($)	Mar. 16, 2018 USD ($)	Jun. 22, 2017 USD ($)	Dec. 07, 2016 USD ($)	May 31, 2018 Loan	Jun. 30, 2018 USD ($) Loan		Jun. 30, 2018 USD ($) Loan shares		Dec. 31, 2017 USD ($) Loan	[2]	Jun. 26, 2018 USD ($)	Mar. 31, 2018 USD ($)
Cash Flow Supplemental Disclosures [Line Items]
Number of Loans | Loan							9		9
Number of loans sold | Loan						1	6		6
Unpaid principal balance							$ 13,000		$ 13,000					$ 90,260
Principal balance							7,017		$ 7,017
Preferred Series D
Cash Flow Supplemental Disclosures [Line Items]
Proceeds from sale of investment	$ 56,765	$ 4,863		$ 10,057	$ 11,600
Liquidation preference													$ 73,480
Variable Interest Entity, Not Primary Beneficiary | Preferred Series D | RAIT FL5 & FL6
Cash Flow Supplemental Disclosures [Line Items]
Shares repurchased and cancelled, shares | shares	2,939,190								2,939,190
Proceeds from sale of investment	$ 56,765								$ 56,765
Variable Interest Entity, Not Primary Beneficiary | Preferred Series A, B, and C | RAIT FL5 & FL6
Cash Flow Supplemental Disclosures [Line Items]
Liquidation preference	$ 16,715						16,715		16,715
Plaz America
Cash Flow Supplemental Disclosures [Line Items]
Acquired the non-controlling interests			$ 343						$ 343
Commercial Portfolio Segment
Cash Flow Supplemental Disclosures [Line Items]
Number of Loans | Loan									65	[1]	123
Unpaid principal balance							733,065	[1]	$ 733,065	[1]	$ 1,273,507
Principal balance							732,623	[1]	732,623	[1]	$ 1,272,951
Commercial Portfolio Segment | Commercial Mortgage Loans Sold
Cash Flow Supplemental Disclosures [Line Items]
Unpaid principal balance							31,377		31,377
Principal balance							$ 31,377		$ 31,377

[1] Includes $96,104 of cash flow loans, of which $45,343 are commercial mortgage loans, $21,130 are mezzanine loans and $29,631 are preferred equity interests. See Note 2: Summary of Significant Accounting Policies, (j) Revenue Recognition, for further discussion of our cash flow loans.

[2] Includes $106,136 of cash flow loans, of which $55,353 are commercial mortgage loans, $21,149 are mezzanine loans and $29,634 are preferred equity interests. See Note 2: Summary of Significant Accounting Policies, (j) Revenue Recognition, for further discussion of our cash flow loans.