Carrying Amount and Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets
Derivative assets	$ 73	$ 11
Liabilities
Junior subordinated notes	7,052	8,121
Carrying Amount
Assets
Total investment in mortgage loans, held for investment, net	1,033,552	1,255,723
Investment in mortgage loans, held for sale	38,394
Cash and cash equivalents	84,483	53,380
Restricted cash	152,962	157,914
Derivative assets	73	11
Carrying Amount \| Recourse Indebtedness \| 7.0% convertible senior notes
Liabilities
Convertible senior notes	834	833
Carrying Amount \| Recourse Indebtedness \| 4.0% convertible senior notes
Liabilities
Convertible senior notes	101,330	106,800
Carrying Amount \| Recourse Indebtedness \| 7.625% senior notes due 2024
Liabilities
Indebtedness	54,926	54,867
Carrying Amount \| Recourse Indebtedness \| 7.125% Senior Notes due 2019
Liabilities
Indebtedness	67,614	67,474
Carrying Amount \| Recourse Indebtedness \| Senior Secured Notes
Liabilities
Indebtedness	9,200	11,063
Carrying Amount \| Recourse Indebtedness \| Junior subordinated notes, at amortized cost
Liabilities
Junior subordinated notes	25,100	25,100
Carrying Amount \| Non Recourse Indebtedness \| CDO notes payable, at amortized cost
Liabilities
Notes payable	209,031	254,724
Carrying Amount \| Non Recourse Indebtedness \| Loan Payable On Real Estate
Liabilities
Loans payable on real estate	61,619	61,922
Carrying Amount \| Other indebtedness
Liabilities
Indebtedness	40,948	40,955
Carrying Amount \| CMBS securitizations \| Non Recourse Indebtedness
Liabilities
Notes payable	694,643	736,586
Carrying Amount \| Junior subordinated notes, at fair value \| Recourse Indebtedness
Liabilities
Junior subordinated notes	7,052	8,121
Carrying Amount \| Secured warehouse facilities
Liabilities
Indebtedness		21,743
Estimated Fair Value
Assets
Total investment in mortgage loans, held for investment, net	996,039	1,252,780
Investment in mortgage loans, held for sale	38,435
Cash and cash equivalents	84,483	53,380
Restricted cash	152,962	157,914
Derivative assets	73	11
Estimated Fair Value \| Recourse Indebtedness \| 7.0% convertible senior notes
Liabilities
Convertible senior notes	544	533
Estimated Fair Value \| Recourse Indebtedness \| 4.0% convertible senior notes
Liabilities
Convertible senior notes	99,214	103,457
Estimated Fair Value \| Recourse Indebtedness \| 7.625% senior notes due 2024
Liabilities
Indebtedness	41,680	43,009
Estimated Fair Value \| Recourse Indebtedness \| 7.125% Senior Notes due 2019
Liabilities
Indebtedness	59,871	61,567
Estimated Fair Value \| Recourse Indebtedness \| Senior Secured Notes
Liabilities
Indebtedness	8,806	11,197
Estimated Fair Value \| Recourse Indebtedness \| Junior subordinated notes, at amortized cost
Liabilities
Junior subordinated notes	7,755	8,849
Estimated Fair Value \| Non Recourse Indebtedness \| CDO notes payable, at amortized cost
Liabilities
Notes payable	152,673	196,212
Estimated Fair Value \| Non Recourse Indebtedness \| Loan Payable On Real Estate
Liabilities
Loans payable on real estate	63,404	64,377
Estimated Fair Value \| Other indebtedness
Liabilities
Indebtedness	40,830	40,830
Estimated Fair Value \| CMBS securitizations \| Non Recourse Indebtedness
Liabilities
Notes payable	700,918	744,359
Estimated Fair Value \| Junior subordinated notes, at fair value \| Recourse Indebtedness
Liabilities
Junior subordinated notes	$ 7,052	8,121
Estimated Fair Value \| Secured warehouse facilities
Liabilities
Indebtedness		$ 22,313

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Fair value of subordinated debt obligations including, but not limited to, subordinated loan, subordinated bond, subordinated debenture or junior debt.

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