Indebtedness - Additional Information (Detail)			1 Months Ended	3 Months Ended		9 Months Ended
		Oct. 17, 2016 USD ($)	Feb. 29, 2016 USD ($)	Sep. 30, 2016 USD ($) $ / shares		Sep. 30, 2016 USD ($) Property $ / shares		Sep. 30, 2015 USD ($)	Jul. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)	Apr. 30, 2016 USD ($)	Apr. 01, 2016 USD ($)	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Payment of notes						$ 243,854,000		$ 273,872,000
Indebtedness				$ 1,975,863,000		1,975,863,000					$ 17,696,000		$ 2,399,475,000
Gains (losses) on extinguishments of debt				(6,000)		998,000
Unpaid Principal Balance				2,012,582,000		2,012,582,000							2,452,567,000
R A I T F L Three | Equity Securities
Debt Instrument [Line Items]
Owned unrated classes of junior notes				37,387,000		37,387,000
R A I T F L Four | Investors | Subsequent Event
Debt Instrument [Line Items]
Collateral repayments		$ 18,000,000
R A I T F L Four | Junior Notes
Debt Instrument [Line Items]
Owned unrated classes of junior notes				41,390,000		41,390,000
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
CMBS securitizations
Debt Instrument [Line Items]
Underlying collateral				618,494,000		618,494,000							$ 885,055,000
CMBS securitizations | R A I T F L Two
Debt Instrument [Line Items]
Underlying collateral				0		0
CMBS securitizations | R A I T F L Three
Debt Instrument [Line Items]
Underlying collateral				115,878,000		115,878,000
CMBS securitizations | R A I T F L Four
Debt Instrument [Line Items]
Underlying collateral				173,888,000		173,888,000
CMBS securitizations | R A I T F L Five
Debt Instrument [Line Items]
Underlying collateral				$ 346,728,000		$ 346,728,000
7.0% convertible senior notes
Debt Instrument [Line Items]
Stated interest rate				7.00%		7.00%							7.00%
4.0% convertible senior notes
Debt Instrument [Line Items]
Stated interest rate				4.00%		4.00%							4.00%
CDO notes payable, at amortized cost
Debt Instrument [Line Items]
Underlying collateral				$ 1,107,924,000		$ 1,107,924,000							$ 1,388,194,000
Loans payable on real estate
Debt Instrument [Line Items]
Line of credit facility, repayments						$ 55,441,000
Number of real estate properties disposed | Property						4
Recourse Indebtedness
Debt Instrument [Line Items]
Indebtedness				509,938,000		$ 509,938,000							484,764,000
Unpaid Principal Balance				532,308,000		532,308,000							$ 514,541,000
Recourse Indebtedness | Floating Rate Loans
Debt Instrument [Line Items]
Line of credit facility, borrowing capacity				100,000,000		100,000,000
Recourse Indebtedness | CMBS securitizations | One Hundred Fifty Thousand CMF One [Member]
Debt Instrument [Line Items]
Indebtedness				77,264,000		77,264,000
Line of credit facility, borrowing capacity									$ 150,000,000
Recourse Indebtedness | CMBS securitizations | Seventy Five Thousand CMF [Member]
Debt Instrument [Line Items]
Indebtedness				48,276,000		48,276,000
Line of credit facility, borrowing capacity				75,000,000		$ 75,000,000
Debt instrument, financial covenant compliance						As of September 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		$ 37,240,000
Line of credit facility, borrowing capacity				$ 150,000,000		$ 150,000,000
Debt instrument, financial covenant compliance						As of September 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%							7.00%
Convertible note conversion rate						190.2627
Principal amount of convertible note, conversion rate				$ 1,000		$ 1,000
Initial conversion price | $ / shares				$ 5.26		$ 5.26
Debt instrument redemption amount												$ 29,177,000
Convertible notes outstanding				$ 871,000		$ 871,000
Aggregate principal amount of notes issued													$ 871,000
Indebtedness				844,000	[1]	844,000	[1]						28,868,000	[2]
Unpaid Principal Balance				$ 871,000	[1]	$ 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%							4.00%
Convertible note conversion rate						108.5803
Principal amount of convertible note, conversion rate				$ 1,000		$ 1,000
Initial conversion price | $ / shares				$ 9.21		$ 9.21
Convertible notes outstanding				$ 126,098,000		$ 126,098,000
Principal amount repurchase convertible senior notes										$ 15,652,000
Consideration from repurchase convertible senior notes										$ 14,075,000
Aggregate principal amount of notes issued													$ 126,098,000
Indebtedness	[3]			119,883,000		119,883,000							133,039,000
Unpaid Principal Balance	[3]			126,098,000		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										$ 2,713,000
Consideration from repurchase convertible senior notes										$ 2,172,000
Senior notes, outstanding				57,287,000		57,287,000
Indebtedness				55,540,000		55,540,000							57,952,000
Unpaid Principal Balance				57,287,000		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										$ 1,174,000
Consideration from repurchase convertible senior notes										$ 1,081,000
Senior notes, outstanding				70,731,000		70,731,000
Indebtedness				69,186,000		69,186,000							69,749,000
Unpaid Principal Balance				70,731,000		70,731,000							71,905,000
Recourse Indebtedness | Senior Secured Notes
Debt Instrument [Line Items]
Senior notes, outstanding				64,000,000		64,000,000
Payment of notes						6,000,000
Indebtedness				59,440,000		59,440,000							63,045,000
Unpaid Principal Balance				64,000,000		64,000,000							70,000,000
Recourse Indebtedness | Junior subordinated notes, at fair value
Debt Instrument [Line Items]
Aggregate principal amount of notes issued				18,671,000		18,671,000
Fair value of indebtedness				11,524,000		11,524,000
Recourse Indebtedness | Two Year CMBS Facilities
Debt Instrument [Line Items]
Indebtedness				0		$ 0
Extended maturity term						2018-07
Debt instrument, financial covenant compliance						As of September 30, 2016, we had $0 of outstanding CMBS borrowings and $77,264 of outstanding commercial mortgage borrowings under the amended and restated master repurchase agreement, or the Amended MRA.
Recourse Indebtedness | Amended Master Repurchase Agreement
Debt Instrument [Line Items]
Line of credit facility, borrowing capacity				200,000,000		$ 200,000,000
Recourse Indebtedness | One Year CMBS Facilities | CMBS securitizations
Debt Instrument [Line Items]
Indebtedness				6,770,000		6,770,000
Line of credit facility, borrowing capacity				150,000,000		$ 150,000,000
Debt instrument, financial covenant compliance						As of September 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				1,441,510,000		$ 1,441,510,000							1,914,711,000
Unpaid Principal Balance				1,455,953,000		1,455,953,000							1,938,026,000
Non-recourse indebtedness | R A I T F L Three
Debt Instrument [Line Items]
Outstanding principal balance of classes of investment grade senior notes				78,491,000		78,491,000
Non-recourse indebtedness | R A I T F L Four
Debt Instrument [Line Items]
Outstanding principal balance of classes of investment grade senior notes				132,498,000		132,498,000
Non-recourse indebtedness | R A I T F L Five
Debt Instrument [Line Items]
Outstanding principal balance of classes of investment grade senior notes				285,924,000		285,924,000
Non-recourse indebtedness | CMBS securitizations
Debt Instrument [Line Items]
Indebtedness				492,493,000	[4]	492,493,000	[4]						708,510,000	[5]
Unpaid Principal Balance				496,913,000	[4]	496,913,000	[4]						717,255,000	[5]
Non-recourse indebtedness | CDO notes payable, at amortized cost
Debt Instrument [Line Items]
Principal amount repurchase convertible senior notes				5,880,000		5,880,000
Consideration from repurchase convertible senior notes				4,988,000		4,988,000
Indebtedness	[7]			719,197,000	[6]	719,197,000	[6]						937,569,000	[8]
Gains (losses) on extinguishments of debt				682,000
Unpaid Principal Balance	[7]			728,362,000	[6]	728,362,000	[6]						950,981,000	[8]
Non-recourse indebtedness | Loans payable on real estate
Debt Instrument [Line Items]
Indebtedness				229,820,000	[9]	229,820,000	[9]						268,632,000
Unpaid Principal Balance				230,678,000	[9]	230,678,000	[9]						$ 269,790,000
Non-recourse indebtedness | Loans payable on real estate | First Mortgage | Mortgage Loan One
Debt Instrument [Line Items]
Unpaid Principal Balance				17,987,000		17,987,000
Investment Grade Senior Notes | R A I T F L Five
Debt Instrument [Line Items]
Outstanding principal balance of classes of investment grade senior notes				$ 23,019,000		$ 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 $618,494 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] Collateralized by $1,107,924 principal amount of commercial mortgage loans, mezzanine loans, other loans and preferred equity interests, $641,118 of which eliminates in consolidation. 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.

[7] Excludes CDO notes payable purchased by us which are eliminated in consolidation.

[8] Collateralized by $1,388,194 principal amount of commercial mortgage loans, mezzanine loans, other loans and preferred equity interests, $815,745 of which eliminates in consolidation. 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.

[9] Certain loans payable on real estate had maturity dates of June 2016. These loans payable on real estate are currently in the process of being refinanced with the lenders.