Carrying Amount and Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2016		Apr. 30, 2016	Dec. 31, 2015		Oct. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets
Total investment in mortgages and loans, net	$ 1,280,285			$ 1,606,486
Cash and cash equivalents	110,531			87,581			$ 106,963	$ 85,513
Restricted cash	190,179			207,599
Derivative assets	206			182
Liabilities
Indebtedness	1,751,082		$ 17,696	2,399,475		$ 82,423
Derivative liabilities				4,727
Junior subordinated notes	11,822			10,504
Warrants and investor SARs	30,400			26,200
Recourse Indebtedness
Liabilities
Indebtedness	365,921			484,764
Non-recourse indebtedness
Liabilities
Indebtedness	1,361,246			1,914,711
CMBS securitizations | Non-recourse indebtedness
Liabilities
Indebtedness	641,077	[1]		708,510	[2]
Carrying Amount
Assets
Total investment in mortgages and loans, net	1,280,285			1,606,486
Cash and cash equivalents	110,531			87,581
Restricted cash	190,179			207,599
Derivative assets	206			182
Liabilities
Indebtedness				63,045
Carrying Amount | 7.0% convertible senior notes
Liabilities
Indebtedness	831			28,868
Carrying Amount | 4.0% convertible senior notes
Liabilities
Indebtedness	120,271			133,039
Carrying Amount | 7.625% senior notes due 2024
Liabilities
Indebtedness	55,568			57,952
Carrying Amount | 7.125% Senior Notes due 2019
Liabilities
Indebtedness	69,188			69,749
Carrying Amount | Senior Secured Notes
Liabilities
Indebtedness	58,233			63,045
Carrying Amount | Junior subordinated notes, at amortized cost
Liabilities
Indebtedness	25,100			24,884
Carrying Amount | CDO notes payable, at amortized cost
Liabilities
Indebtedness	534,501			937,569
Carrying Amount | Loans payable on real estate
Liabilities
Indebtedness	185,668			268,632
Carrying Amount | Derivative Liabilities
Liabilities
Derivative liabilities				4,727
Carrying Amount | Warrants and investor SARs
Liabilities
Warrants and investor SARs	30,400			26,200
Carrying Amount | Recourse Indebtedness | 7.0% convertible senior notes
Liabilities
Indebtedness	831			28,868
Carrying Amount | Recourse Indebtedness | 4.0% convertible senior notes
Liabilities
Indebtedness	120,271			133,039
Carrying Amount | Recourse Indebtedness | 7.625% senior notes due 2024
Liabilities
Indebtedness	55,568			57,952
Carrying Amount | Recourse Indebtedness | 7.125% Senior Notes due 2019
Liabilities
Indebtedness	69,188			69,749
Carrying Amount | Recourse Indebtedness | Senior Secured Notes
Liabilities
Indebtedness	58,233
Carrying Amount | Recourse Indebtedness | Junior subordinated notes, at amortized cost
Liabilities
Indebtedness	25,100			24,884
Carrying Amount | Recourse Indebtedness | CMBS Facilities
Liabilities
Indebtedness	24,908			96,723
Carrying Amount | Non-recourse indebtedness | CDO notes payable, at amortized cost
Liabilities
Indebtedness	534,501			937,569
Carrying Amount | Non-recourse indebtedness | Loans payable on real estate
Liabilities
Indebtedness	185,668			268,632
Carrying Amount | Other indebtedness
Liabilities
Indebtedness	23,915
Carrying Amount | CMBS securitizations
Liabilities
Indebtedness	641,077			708,510
Carrying Amount | CMBS securitizations | Non-recourse indebtedness
Liabilities
Indebtedness	641,077			708,510
Estimated Fair Value
Assets
Total investment in mortgages and loans, net	1,256,342			1,537,086
Cash and cash equivalents	110,531			87,581
Restricted cash	190,179			207,599
Derivative assets	206			182
Estimated Fair Value | Derivative Liabilities
Liabilities
Derivative liabilities				4,727
Estimated Fair Value | Warrants and investor SARs
Liabilities
Warrants and investor SARs	30,400			26,200
Estimated Fair Value | Recourse Indebtedness | 7.0% convertible senior notes
Liabilities
Convertible senior notes, Estimated Fair Value	890			27,795
Estimated Fair Value | Recourse Indebtedness | 4.0% convertible senior notes
Liabilities
Convertible senior notes, Estimated Fair Value	116,861			104,184
Estimated Fair Value | Recourse Indebtedness | 7.625% senior notes due 2024
Liabilities
Senior notes, Estimated Fair Value	53,231			46,560
Estimated Fair Value | Recourse Indebtedness | 7.125% Senior Notes due 2019
Liabilities
Senior notes, Estimated Fair Value	69,118			62,471
Estimated Fair Value | Recourse Indebtedness | Senior Secured Notes
Liabilities
Senior notes, Estimated Fair Value	62,620			66,725
Estimated Fair Value | Recourse Indebtedness | Junior subordinated notes, at amortized cost
Liabilities
Junior subordinated notes	13,099			11,221
Estimated Fair Value | Recourse Indebtedness | CMBS Facilities
Liabilities
Indebtedness	26,421			97,067
Estimated Fair Value | Non-recourse indebtedness | CDO notes payable, at amortized cost
Liabilities
Notes payable, Estimated Fair Value	477,032			801,289
Estimated Fair Value | Non-recourse indebtedness | Loans payable on real estate
Liabilities
Loans payable on real estate, Estimated Fair Value	188,525			281,840
Estimated Fair Value | Other indebtedness
Liabilities
Indebtedness	24,321
Estimated Fair Value | CMBS securitizations | Non-recourse indebtedness
Liabilities
Notes payable, Estimated Fair Value	646,642			709,001
Junior subordinated notes, at fair value | Carrying Amount | Recourse Indebtedness
Liabilities
Indebtedness	11,822			10,504
Junior subordinated notes, at fair value | Estimated Fair Value | Recourse Indebtedness
Liabilities
Junior subordinated notes	$ 11,822			$ 10,504

[1] Collateralized by $789,421 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.

[2] 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