Indebtedness - Additional Information (Detail)				1 Months Ended					6 Months Ended			12 Months Ended
		Jun. 24, 2016 USD ($)	Sep. 17, 2015 USD ($) Option	May 31, 2016 USD ($) MortgageLoan	Apr. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Feb. 29, 2016 USD ($)	Jan. 31, 2016 USD ($)	Jun. 30, 2016 USD ($) $ / shares		Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)		Jul. 31, 2016 USD ($)	Apr. 01, 2016 USD ($)
Debt Instrument [Line Items]
Payment of notes									$ 242,755,000		$ 20,640,000
Indebtedness					$ 17,696,000				3,005,259,000			$ 3,328,082,000
Unpaid Principal Balance									3,055,452,000			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							$ 24,796,000
Equity interest | R A I T F L Two
Debt Instrument [Line Items]
Real estate investment									40,191,000
Equity interest | R A I T F L Three
Debt Instrument [Line Items]
Real estate investment									37,387,000
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									772,557,000			$ 885,055,000
CMBS securitizations | R A I T F L Two
Debt Instrument [Line Items]
Real estate investment									110,425,000
CMBS securitizations | R A I T F L Three
Debt Instrument [Line Items]
Real estate investment									125,878,000
CMBS securitizations | R A I T F L Four
Debt Instrument [Line Items]
Real estate investment									189,504,000
CMBS securitizations | R A I T F L Five
Debt Instrument [Line Items]
Real estate investment									$ 346,728,000
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]
Interest rate on excess of reference rate									2.45%			2.45%
Term Loan One
Debt Instrument [Line Items]
Line of credit facility, repayments				$ 30,000,000	30,000,000
Loans payable on real estate
Debt Instrument [Line Items]
Line of credit facility, repayments						$ 43,694,000	6,659,000
Recourse Indebtedness
Debt Instrument [Line Items]
Indebtedness									$ 479,608,000			$ 484,764,000
Unpaid Principal Balance									503,735,000			$ 514,541,000
Recourse Indebtedness | Floating Rate Loans
Debt Instrument [Line Items]
Line of credit facility, borrowing capacity									100,000,000
Recourse Indebtedness | CMBS securitizations | One Hundred Fifty Thousand CMF One [Member]
Debt Instrument [Line Items]
Indebtedness									26,131,000
Line of credit facility, borrowing capacity														$ 150,000,000
Recourse Indebtedness | CMBS securitizations | Seventy Five Thousand CMF [Member]
Debt Instrument [Line Items]
Indebtedness									49,179,000
Line of credit facility, borrowing capacity									$ 75,000,000
Debt instrument, financial covenant compliance									As of June 30, 2016, we were in compliance with all financial covenants contained in the $75,000 commercial mortgage facility.
Recourse Indebtedness | CMBS securitizations | One Hundred Fifty Thousand CMF Two [Member]
Debt Instrument [Line Items]
Indebtedness									$ 37,240,000
Line of credit facility, borrowing capacity									$ 150,000,000
Debt instrument, financial covenant compliance									As of June 30, 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									184.9115
Principal amount of convertible note, conversion rate									$ 1,000
Initial conversion price | $ / shares									$ 5.41
Debt instrument redemption amount															$ 29,177,000
Convertible notes outstanding															$ 871,000
Aggregate principal amount of notes issued												$ 871,000
Indebtedness									$ 843,000	[1]		28,868,000	[2]
Unpaid Principal Balance									$ 871,000	[1]		$ 30,048,000	[2]
Recourse Indebtedness | 4.0% convertible senior notes
Debt Instrument [Line Items]
Stated interest rate									4.00%			4.00%
Convertible note conversion rate									108.5803
Principal amount of convertible note, conversion rate									$ 1,000
Initial conversion price | $ / shares									$ 9.21
Convertible notes outstanding									$ 126,098
Principal amount repurchase convertible senior notes									15,652
Consideration from repurchase convertible senior notes									14,075
Aggregate principal amount of notes issued												$ 126,098,000
Indebtedness	[3]								119,474,000			133,039,000
Unpaid Principal Balance	[3]								$ 126,098,000			141,750,000
Recourse Indebtedness | 7.625% senior notes due 2024
Debt Instrument [Line Items]
Stated interest rate									7.625%
Principal amount repurchase convertible senior notes									$ 2,713
Consideration from repurchase convertible senior notes									2,172
Senior notes, outstanding									57,287
Indebtedness									55,450,000			57,952,000
Unpaid Principal Balance									$ 57,287,000			60,000,000
Recourse Indebtedness | 7.125% Senior Notes due 2019
Debt Instrument [Line Items]
Stated interest rate									7.125%
Principal amount repurchase convertible senior notes									$ 1,174
Consideration from repurchase convertible senior notes									1,081
Senior notes, outstanding									70,731
Indebtedness									68,899,000			69,749,000
Unpaid Principal Balance									70,731,000			71,905,000
Recourse Indebtedness | Senior Secured Notes
Debt Instrument [Line Items]
Senior notes, outstanding									66,000,000
Payment of notes									4,000,000
Indebtedness									60,645,000			63,045,000
Unpaid Principal Balance									66,000,000			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									10,789,000
Recourse Indebtedness | Two Year CMBS Facilities
Debt Instrument [Line Items]
Indebtedness									$ 3,285,000
Extended maturity term									2018-07
Debt instrument, financial covenant compliance									As of June 30, 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									23,142,000
Line of credit facility, borrowing capacity									$ 150,000,000
Debt instrument, financial covenant compliance									As of June 30, 2016, we were in compliance with all financial covenants contained in the $150,000 CMBS facility.
Non-recourse indebtedness
Debt Instrument [Line Items]
Indebtedness									$ 2,501,130,000			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									extended for two 12-month terms
Line of credit facility, number of options available for extension | Option			2
Unpaid Principal Balance									$ 2,526,921,000			2,875,482,000
Non-recourse indebtedness | R A I T F L Two
Debt Instrument [Line Items]
Real estate investment									70,234,000
Non-recourse indebtedness | R A I T F L Three
Debt Instrument [Line Items]
Real estate investment									88,491,000
Non-recourse indebtedness | R A I T F L Four
Debt Instrument [Line Items]
Real estate investment									148,114,000
Non-recourse indebtedness | R A I T F L Five
Debt Instrument [Line Items]
Real estate investment									$ 285,924,000
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									$ 586,977,000	[4]		708,510,000	[5]
Unpaid Principal Balance									$ 592,768,000	[4]		717,255,000	[5]
Non-recourse indebtedness | Secured credit facilities
Debt Instrument [Line Items]
Stated interest rate									0.25%
Indebtedness									$ 243,604,000	[6]		267,155,000	[7]
Line of credit facility, remaining borrowing capacity									77,665,000
Line of credit, drew down						8,000,000
Line of credit facility, repayments				77,665,000		6,000,000
Line of credit, additional drew down						$ 45,476,000
Unpaid Principal Balance									$ 247,335,000	[6]		271,500,000	[7]
Non-recourse indebtedness | Term Loan One
Debt Instrument [Line Items]
Line of credit facility, borrowing capacity		$ 40,000,000	$ 120,000,000
Maturity date		Sep. 17, 2018
Line of credit facility, repayments		$ 33,512,000		$ 26,704,000			$ 23,784,000	$ 23,784,000
Required to reduce the principal amount outstanding per month		$ 100,000
Required percentage of proceeds from equity issuances, sales of assets, or refinancing of assets to use for repayment of debt		50.00%
Line of credit facility, payment terms									The term loan requires monthly payments of interest only through June 30, 2017. IROP is required to reduce the principal amount outstanding under the term loan by $100 per month beginning July 2017 and must apply 50% of all net proceeds from equity issuances, sales of assets, or refinancings of assets towards repaying the amended term loan.
Interest rate, description									bear interest at a rate equal to either (i) the LIBOR rate plus a margin of 400 basis points, or (ii) a base rate plus a margin of 300 basis points.
Payment of closing costs		$ 416,000
Line of credit									$ 40,000,000
Non-recourse indebtedness | Term Loan One | Property one
Debt Instrument [Line Items]
Property fixed rate mortgage period				7 years
Non-recourse indebtedness | Term Loan One | Property two
Debt Instrument [Line Items]
Property fixed rate mortgage period				10 years
Non-recourse indebtedness | Term Loan One | London Interest Bank Offer Rate
Debt Instrument [Line Items]
Interest rate on excess of reference rate		4.00%							4.00%
Non-recourse indebtedness | Term Loan One | Base Rate
Debt Instrument [Line Items]
Interest rate on excess of reference rate		3.00%
Non-recourse indebtedness | Loans payable on real estate
Debt Instrument [Line Items]
Indebtedness									$ 865,691,000	[8]		811,666,000	[9]
Unpaid Principal Balance									870,716,000	[8]		$ 815,746,000	[9]
Non-recourse indebtedness | Loans payable on real estate | First Mortgage
Debt Instrument [Line Items]
Number of mortgages obtained | MortgageLoan				3
Non-recourse indebtedness | Loans payable on real estate | First Mortgage | Mortgage Loan One
Debt Instrument [Line Items]
Unpaid Principal Balance				$ 25,050,000
Contractual Maturity, start year				2023-06
Non-recourse indebtedness | Loans payable on real estate | First Mortgage | Mortgage Loan One | Minimum
Debt Instrument [Line Items]
Stated interest rate				3.40%
Non-recourse indebtedness | Loans payable on real estate | First Mortgage | Mortgage Loan Two
Debt Instrument [Line Items]
Unpaid Principal Balance				$ 31,250,000
Contractual Maturity, start year				2023-06
Non-recourse indebtedness | Loans payable on real estate | First Mortgage | Mortgage Loan Two | Minimum
Debt Instrument [Line Items]
Stated interest rate				3.28%
Non-recourse indebtedness | Loans payable on real estate | First Mortgage | Mortgage Loan Three
Debt Instrument [Line Items]
Unpaid Principal Balance				$ 49,680,000
Contractual Maturity, start year				2026-06
Non-recourse indebtedness | Loans payable on real estate | First Mortgage | Mortgage Loan Three | Minimum
Debt Instrument [Line Items]
Stated interest rate				3.70%
Investment Grade Senior Notes | R A I T F L Five
Debt Instrument [Line Items]
Real estate investment					$ 23,019,000				$ 23,019,000

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

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

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

[4] Collateralized by $772,557 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] 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.

[6] Floating rate at 245 basis points over 1-month LIBOR.

[7] Floating rate at 245 basis points over 1-month LIBOR.

[8] Includes $601,047 of unpaid principal balance and $597,125 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 June 2026.

[9] 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.