Carrying Amount and Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Assets
Derivative assets	$ 85
Liabilities
Junior subordinated notes	12,524	$ 11,822
Fair Value of Liabilities	17
Warrants and investor SARs	27,500	30,400
Carrying Amount
Assets
Total investment in mortgages and loans, net	1,244,191	1,280,285
Cash and cash equivalents	89,317	110,531
Restricted cash	193,580	190,179
Derivative assets	85	206
Carrying Amount \| Derivative Liabilities
Liabilities
Fair Value of Liabilities	17
Carrying Amount \| Warrants and investor SARs
Liabilities
Warrants and investor SARs	27,500	30,400
Carrying Amount \| Recourse Indebtedness \| 7.0% convertible senior notes
Liabilities
Convertible senior notes	832	831
Carrying Amount \| Recourse Indebtedness \| 4.0% convertible senior notes
Liabilities
Convertible senior notes	121,065	120,271
Carrying Amount \| Recourse Indebtedness \| 7.625% senior notes due 2024
Liabilities
Indebtedness	55,687	55,568
Carrying Amount \| Recourse Indebtedness \| 7.125% Senior Notes due 2019
Liabilities
Indebtedness	69,477	69,188
Carrying Amount \| Recourse Indebtedness \| Senior Secured Notes
Liabilities
Indebtedness	14,355	58,233
Carrying Amount \| Recourse Indebtedness \| Junior subordinated notes, at amortized cost
Liabilities
Junior subordinated notes	25,100	25,100
Carrying Amount \| Recourse Indebtedness \| CMBS Facilities
Liabilities
Indebtedness	29,818	24,908
Carrying Amount \| Non-recourse indebtedness \| CDO notes payable, at amortized cost
Liabilities
Notes payable	370,379	534,501
Carrying Amount \| Non-recourse indebtedness \| Loans payable on real estate
Liabilities
Loans payable on real estate	134,687	185,668
Carrying Amount \| Other indebtedness
Liabilities
Indebtedness	40,880	23,915
Carrying Amount \| CMBS securitizations \| Non-recourse indebtedness
Liabilities
Notes payable	713,263	641,077
Carrying Amount \| Junior subordinated notes, at fair value \| Recourse Indebtedness
Liabilities
Junior subordinated notes	12,524	11,822
Estimated Fair Value
Assets
Total investment in mortgages and loans, net	1,192,723	1,256,342
Cash and cash equivalents	89,317	110,531
Restricted cash	193,580	190,179
Derivative assets	85	206
Estimated Fair Value \| Derivative Liabilities
Liabilities
Fair Value of Liabilities	17
Estimated Fair Value \| Warrants and investor SARs
Liabilities
Warrants and investor SARs	27,500	30,400
Estimated Fair Value \| Recourse Indebtedness \| 7.0% convertible senior notes
Liabilities
Convertible senior notes	590	890
Estimated Fair Value \| Recourse Indebtedness \| 4.0% convertible senior notes
Liabilities
Convertible senior notes	119,680	116,861
Estimated Fair Value \| Recourse Indebtedness \| 7.625% senior notes due 2024
Liabilities
Indebtedness	55,018	53,231
Estimated Fair Value \| Recourse Indebtedness \| 7.125% Senior Notes due 2019
Liabilities
Indebtedness	70,420	69,118
Estimated Fair Value \| Recourse Indebtedness \| Senior Secured Notes
Liabilities
Indebtedness	15,783	62,620
Estimated Fair Value \| Recourse Indebtedness \| Junior subordinated notes, at amortized cost
Liabilities
Junior subordinated notes	13,995	13,099
Estimated Fair Value \| Recourse Indebtedness \| CMBS Facilities
Liabilities
Indebtedness	30,708	26,421
Estimated Fair Value \| Non-recourse indebtedness \| CDO notes payable, at amortized cost
Liabilities
Notes payable	329,004	477,032
Estimated Fair Value \| Non-recourse indebtedness \| Loans payable on real estate
Liabilities
Loans payable on real estate	137,583	188,525
Estimated Fair Value \| Other indebtedness
Liabilities
Indebtedness	40,830	24,321
Estimated Fair Value \| CMBS securitizations \| Non-recourse indebtedness
Liabilities
Notes payable	721,456	646,642
Estimated Fair Value \| Junior subordinated notes, at fair value \| Recourse Indebtedness
Liabilities
Junior subordinated notes	$ 12,524	$ 11,822

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