Indebtedness - Additional Information (Detail)				1 Months Ended		3 Months Ended			12 Months Ended
		May. 10, 2016 USD ($)	Sep. 17, 2015 USD ($) Option	Apr. 30, 2016 USD ($)	Feb. 29, 2016 USD ($)	Mar. 31, 2016 USD ($) $ / shares		Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)		Apr. 01, 2016 USD ($)
Debt Instrument [Line Items]
Payment of notes						$ 74,266,000		$ 19,629,000
Indebtedness						3,267,230,000			$ 3,328,082,000
Unpaid Principal Balance						3,324,228,000			3,390,023,000
R A I T F L Five
Debt Instrument [Line Items]
Percentage of ownership in joint venture					60.00%
Proceeds from contribution of junior notes					$ 24,800,000
Equity interest | R A I T F L Two
Debt Instrument [Line Items]
Real estate investment						40,188,000
Equity interest | R A I T F L Three
Debt Instrument [Line Items]
Real estate investment						37,386,000
Junior Notes | R A I T F L Four
Debt Instrument [Line Items]
Real estate investment						41,390,000
CMBS securitizations
Debt Instrument [Line Items]
Indebtedness						855,555,000			$ 885,055,000
CMBS securitizations | R A I T F L Two
Debt Instrument [Line Items]
Real estate investment						134,725,000
CMBS securitizations | R A I T F L Three
Debt Instrument [Line Items]
Real estate investment						168,278,000
CMBS securitizations | R A I T F L Four
Debt Instrument [Line Items]
Real estate investment						219,284,000
CMBS securitizations | R A I T F L Five
Debt Instrument [Line Items]
Real estate investment						$ 347,446,000
7.0% convertible senior notes
Debt Instrument [Line Items]
Stated interest rate						7.00%			7.00%
4.0% convertible senior notes
Debt Instrument [Line Items]
Stated interest rate						4.00%			4.00%
Secured credit facilities | London Interest Bank Offer Rate
Debt Instrument [Line Items]
Stated interest rate						0.43725%			0.4295%
Interest rate on excess of reference rate						2.45%			2.45%
Term Loan One | Subsequent Event
Debt Instrument [Line Items]
Line of credit facility, repayments		$ 18,400,000
Recourse Indebtedness
Debt Instrument [Line Items]
Indebtedness						$ 509,466,000			$ 484,764,000
Unpaid Principal Balance						538,275,000			$ 514,541,000
Recourse Indebtedness | Floating Rate Loans
Debt Instrument [Line Items]
Line of credit facility, borrowing capacity						100,000,000
Recourse Indebtedness | Seventy Five Thousand CMF [Member] | CMBS securitizations
Debt Instrument [Line Items]
Indebtedness						40,179,000
Line of credit facility, borrowing capacity						$ 75,000,000
Debt instrument, financial covenant compliance						As of March 31, 2016, we were in compliance with all financial covenants contained in the $75,000 commercial mortgage facility.
Recourse Indebtedness | One Hundred Fifty Thousand CMF One [Member] | CMBS securitizations
Debt Instrument [Line Items]
Indebtedness						$ 26,131,000
Line of credit facility, borrowing capacity						$ 150,000,000
Debt instrument, financial covenant compliance						As of March 31, 2016, we were in compliance with all financial covenants contained in the $150,000 commercial mortgage facility.
Recourse Indebtedness | One Hundred Fifty Thousand CMF Two [Member] | CMBS securitizations
Debt Instrument [Line Items]
Indebtedness						$ 15,520,000
Line of credit facility, borrowing capacity						$ 150,000,000
Debt instrument, financial covenant compliance						As of March 31, 2016, we were in compliance with all financial covenants contained in the $150,000 commercial mortgage facility.
Recourse Indebtedness | 7.0% convertible senior notes
Debt Instrument [Line Items]
Stated interest rate						7.00%			7.00%
Convertible note conversion rate						179.4009
Principal amount of convertible note, conversion rate						$ 1,000
Initial conversion price | $ / shares						$ 5.57
Aggregate principal amount of notes issued									$ 30,048,000
Indebtedness	[1]					$ 29,004,000			28,868,000
Unpaid Principal Balance	[1]					$ 30,048,000			$ 30,048,000
Recourse Indebtedness | 7.0% convertible senior notes | Subsequent Event
Debt Instrument [Line Items]
Debt instrument redemption amount											$ 29,177,000
Convertible notes outstanding											$ 871,000
Recourse Indebtedness | 4.0% convertible senior notes
Debt Instrument [Line Items]
Stated interest rate									4.00%
Convertible note conversion rate						1.085803
Principal amount of convertible note, conversion rate						$ 1,000
Initial conversion price | $ / shares						$ 9.21
Aggregate principal amount of notes issued									$ 141,750,000
Indebtedness	[2]					$ 133,763,000			133,039,000
Unpaid Principal Balance	[2]					141,750,000			141,750,000
Recourse Indebtedness | Senior Secured Notes
Debt Instrument [Line Items]
Payment of notes						2,000,000
Senior notes, outstanding						68,000,000
Indebtedness						61,847,000			63,045,000
Unpaid Principal Balance						68,000,000			70,000,000
Recourse Indebtedness | Junior subordinated notes, at fair value
Debt Instrument [Line Items]
Aggregate principal amount of notes issued						18,671,000
Fair value of indebtedness						9,785,000
Recourse Indebtedness | Two Year CMBS Facilities
Debt Instrument [Line Items]
Indebtedness						$ 5,475,000
Debt instrument, financial covenant compliance						As of March 31, 2016, we were in compliance with all financial covenants contained in the Amended MRA.
Recourse Indebtedness | Amended Master Repurchase Agreement
Debt Instrument [Line Items]
Line of credit facility, borrowing capacity						$ 200,000,000
Recourse Indebtedness | One Year CMBS Facilities | CMBS securitizations
Debt Instrument [Line Items]
Indebtedness						35,496,000
Line of credit facility, borrowing capacity						$ 150,000,000
Debt instrument, financial covenant compliance						As of March 31, 2016, we were in compliance with all financial covenants contained in the $150,000 CMBS facility.
Non-recourse indebtedness
Debt Instrument [Line Items]
Indebtedness						$ 2,733,169,000			2,843,318,000
Line of credit facility, borrowing capacity			$ 325,000,000
Right to increase line of credit facility maximum borrowing capacity			$ 450,000,000
Maturity date			Sep. 17, 2018
Line of credit facility, expiration period extension term						option of IROP may be extended for two additional 12-month periods under certain circumstances
Line of credit facility, number of options available for extension | Option			2
Unpaid Principal Balance						$ 2,761,632,000			2,875,482,000
Non-recourse indebtedness | R A I T F L Two
Debt Instrument [Line Items]
Real estate investment						94,537,000
Non-recourse indebtedness | R A I T F L Three
Debt Instrument [Line Items]
Real estate investment						130,892,000
Non-recourse indebtedness | R A I T F L Four
Debt Instrument [Line Items]
Real estate investment						177,894,000
Non-recourse indebtedness | R A I T F L Five
Debt Instrument [Line Items]
Real estate investment						$ 263,624,000
Non-recourse indebtedness | London Interest Bank Offer Rate
Debt Instrument [Line Items]
Interest rate on excess of reference rate						2.45%
Non-recourse indebtedness | CMBS securitizations
Debt Instrument [Line Items]
Indebtedness						$ 660,139,000	[3]		708,510,000	[4]
Unpaid Principal Balance						666,947,000	[3]		717,255,000	[4]
Non-recourse indebtedness | Secured credit facilities
Debt Instrument [Line Items]
Indebtedness						320,855,000	[5]		267,155,000	[6]
Line of credit facility, remaining borrowing capacity						23,000
Unpaid Principal Balance						$ 324,977,000	[5]		271,500,000	[6]
Non-recourse indebtedness | Term Loan One
Debt Instrument [Line Items]
Line of credit facility, borrowing capacity			$ 120,000,000
Maturity date			Sep. 16, 2016
Line of credit facility, expiration period extension term						The KeyBank interim facility may be extended at the option of IROP for an additional six months under certain circumstances
Line of credit facility, payment terms						The KeyBank interim facility requires monthly payments of interest only. IROP must apply 100% of all net proceeds from equity issuances, sales of assets, or refinancings of assets towards repaying the KeyBank interim facility.
Required percentage of proceeds from equity issuances, sales of assets, or refinancing of assets to use for repayment of debt			100.00%
Non-recourse indebtedness | Term Loan One | London Interest Bank Offer Rate
Debt Instrument [Line Items]
Interest rate on excess of reference rate						5.00%
Non-recourse indebtedness | Term Loan One | Subsequent Event
Debt Instrument [Line Items]
Line of credit facility, repayments				$ 11,600,000
Non-recourse indebtedness | Loans payable on real estate
Debt Instrument [Line Items]
Indebtedness						$ 757,668,000	[7]		811,666,000	[8]
Unpaid Principal Balance						761,767,000	[7]		$ 815,746,000	[8]
Investment Grade Senior Notes | R A I T F L Five
Debt Instrument [Line Items]
Real estate investment						$ 23,019,000
Investment Grade Senior Notes | Subsequent Event | R A I T F L Five
Debt Instrument [Line Items]
Real estate investment				$ 23,019,000

[1] Our 7.0% convertible senior notes are redeemable at par, at the option of the holder, in April 2016, April 2021, and April 2026.

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

[3] Excludes the RAIT FL2 junior notes, RAIT FL3 junior notes, RAIT FL4 junior notes and RAIT FL5 junior notes purchased by us which are eliminated in consolidation. Collateralized by $855,555 principal amount of commercial mortgages loans and participation interests. These obligations were issued by separate legal entities and consequently the assets of the special purpose entities that collateralize these obligations are not available to our creditors.

[4] Excludes the RAIT FL2 junior notes, RAIT FL3 junior notes, RAIT FL4 junior notes and RAIT FL5 junior notes purchased by us which are eliminated in consolidation. Collateralized by $885,055 principal amount of commercial mortgage loans and participation interests. These obligations were issued by separate legal entities and consequently the assets of the special purpose entities that collateralize these obligations are not available to our creditors.

[5] Floating rate at 245 basis points over 1-month LIBOR. As of March 31, 2016, 1-month LIBOR was 0.43725%. Interest only payments are due monthly.

[6] Floating rate at 245 basis points over 1-month LIBOR. As of December 31, 2015, 1-month LIBOR was 0.4295%. Interest only payments are due monthly.

[7] Includes $495,253 of unpaid principal balance and $492,129 of carrying amount, respectively, of third party mortgage indebtedness that encumbers properties owned by IRT. The weighted-average interest rate is 3.8% and has a range of maturity dates from January 2021 to May 2025.

[8] Includes $545,956 of unpaid principal balance and $543,080 of carrying amount of third party mortgage indebtedness that encumbers properties owned by IRT. The weighted-average interest rate is 3.8% and has a range of maturity dates from April 2016 to May 2025.