Valuation (Fair Value Measurement Using Significant Unobservable Inputs) (Details) - Level 3 [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	$ 661,588	$ 523,837
Assets, Accreted Discounts/Amortized Premiums	(32,013)	(26,697)
Assets, Realized Gain (Loss)	15,518	4,999
Assets, Change In Net Unrealized Gain/(Loss)	4,536	24,585
Assets, Purchases	937,646	638,520
Assets, Sales	(440,209)	(453,628)
Assets, Transfers into Level 3	13,649	14,021
Assets, Transfers out of Level 3	(34,637)	(64,049)
Assets, Ending Balance	1,126,078	661,588
Liabilities, Begining Balance	(125,105)	(505)
Liabilities, Accreted Discounts/Amortized Premiums		0
Liabilities, Realized Gain/(Loss)		(1,425)
Liabilities, Change In Net Unrealized Gain/(Loss)		1,188
Liabilities Purchases/Payments		1,308
Liabilities, Sales/Issuance		(125,671)
Liabilities, Transfers into Level 3		0
Liabilities, Transfers out of Level 3		0
Liabilities, Ending Balance		(125,105)
Other secured borrowings [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities, Begining Balance	(125,105)	0
Liabilities, Accreted Discounts/Amortized Premiums	0	0
Liabilities, Realized Gain/(Loss)	0	0
Liabilities, Change In Net Unrealized Gain/(Loss)	758	0
Liabilities Purchases/Payments	49,731	0
Liabilities, Sales/Issuance	223,332	125,105
Liabilities, Transfers into Level 3	0	0
Liabilities, Transfers out of Level 3	0	0
Liabilities, Ending Balance	(297,948)	(125,105)
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	800
Financial Derivatives - Liabilities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities, Begining Balance	0	(505)
Liabilities, Accreted Discounts/Amortized Premiums		0
Liabilities, Realized Gain/(Loss)		(1,425)
Liabilities, Change In Net Unrealized Gain/(Loss)		1,188
Liabilities Purchases/Payments		1,308
Liabilities, Sales/Issuance		(566)
Liabilities, Transfers into Level 3		0
Liabilities, Transfers out of Level 3		0
Liabilities, Ending Balance		0
Total Return Swaps [Member] | Financial Derivatives - Liabilities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities, Begining Balance	0	(249)
Liabilities, Accreted Discounts/Amortized Premiums		0
Liabilities, Realized Gain/(Loss)		(554)
Liabilities, Change In Net Unrealized Gain/(Loss)		249
Liabilities, Purchases		572
Liabilities, Sales		(18)
Liabilities, Transfers into Level 3		0
Liabilities, Transfers out of Level 3		0
Liabilities, Ending Balance		0
Credit Default Swaps On Asset Backed Securities [Member] | Financial Derivatives - Liabilities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities, Begining Balance	0	(256)
Liabilities, Accreted Discounts/Amortized Premiums		0
Liabilities, Realized Gain/(Loss)		(871)
Liabilities, Change In Net Unrealized Gain/(Loss)		939
Liabilities, Purchases		736
Liabilities, Sales		(548)
Liabilities, Transfers into Level 3		0
Liabilities, Transfers out of Level 3		0
Liabilities, Ending Balance		0
Other secured borrowings [Member] | Other secured borrowings [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities, Begining Balance	(125,105)	0
Liabilities, Accreted Discounts/Amortized Premiums	0	0
Liabilities, Realized Gain/(Loss)	0	0
Liabilities, Change In Net Unrealized Gain/(Loss)	758	0
Liabilities, Payments	49,731	0
Liabilities, Issuances	(223,332)	(125,105)
Liabilities, Transfers into Level 3	0	0
Liabilities, Transfers out of Level 3	0	0
Liabilities, Ending Balance	(297,948)	(125,105)
Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	658,448	518,250
Assets, Accreted Discounts/Amortized Premiums	(32,013)	(26,697)
Assets, Realized Gain (Loss)	16,205	4,605
Assets, Change In Net Unrealized Gain/(Loss)	3,821	25,948
Assets, Purchases	937,544	638,382
Assets, Sales	(438,411)	(452,012)
Assets, Transfers into Level 3	13,649	14,021
Assets, Transfers out of Level 3	(34,637)	(64,049)
Assets, Ending Balance	1,124,606	658,448
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	5,300	10,600
Investments [Member] | Agency residential mortgage-backed securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	6,173	29,622
Assets, Accreted Discounts/Amortized Premiums	(2,233)	(9,356)
Assets, Realized Gain (Loss)	(10)	(956)
Assets, Change In Net Unrealized Gain/(Loss)	175	(165)
Assets, Purchases	2,753	3,867
Assets, Sales	(1,169)	(153)
Assets, Transfers into Level 3	2,616	0
Assets, Transfers out of Level 3	(1,012)	(16,686)
Assets, Ending Balance	7,293	6,173
Investments [Member] | Private Label Residential Mortgage-Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	101,297	90,083
Assets, Accreted Discounts/Amortized Premiums	383	2,203
Assets, Realized Gain (Loss)	1,838	763
Assets, Change In Net Unrealized Gain/(Loss)	(2,135)	9,498
Assets, Purchases	75,685	68,724
Assets, Sales	(78,487)	(54,690)
Assets, Transfers into Level 3	7,074	14,021
Assets, Transfers out of Level 3	(14,364)	(29,305)
Assets, Ending Balance	91,291	101,297
Investments [Member] | Private Label Commercial Mortgage-Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	12,347	43,268
Assets, Accreted Discounts/Amortized Premiums	(243)	469
Assets, Realized Gain (Loss)	2,229	(3,596)
Assets, Change In Net Unrealized Gain/(Loss)	2,120	8,654
Assets, Purchases	1,481	6,661
Assets, Sales	(16,896)	(37,665)
Assets, Transfers into Level 3	0	0
Assets, Transfers out of Level 3	(235)	(5,444)
Assets, Ending Balance	803	12,347
Investments [Member] | Commercial Mortgage Loans [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	108,301	61,129
Assets, Accreted Discounts/Amortized Premiums	790	921
Assets, Realized Gain (Loss)	1,146	419
Assets, Change In Net Unrealized Gain/(Loss)	1,944	1,957
Assets, Purchases	149,053	78,333
Assets, Sales	(50,049)	(34,458)
Assets, Transfers into Level 3	0	0
Assets, Transfers out of Level 3	0	0
Assets, Ending Balance	211,185	108,301
Investments [Member] | Residential Mortgage Loans [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	182,472	84,290
Assets, Accreted Discounts/Amortized Premiums	(1,965)	(599)
Assets, Realized Gain (Loss)	1,011	1,602
Assets, Change In Net Unrealized Gain/(Loss)	(34)	3,536
Assets, Purchases	402,235	140,535
Assets, Sales	(86,889)	(46,892)
Assets, Transfers into Level 3	0	0
Assets, Transfers out of Level 3	0	0
Assets, Ending Balance	496,830	182,472
Investments [Member] | Collateralized Loan Obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	24,911	44,956
Assets, Accreted Discounts/Amortized Premiums	(351)	(6,833)
Assets, Realized Gain (Loss)	317	2,233
Assets, Change In Net Unrealized Gain/(Loss)	(2,268)	2,606
Assets, Purchases	33,549	71,338
Assets, Sales	(33,115)	(76,775)
Assets, Transfers into Level 3	3,959	0
Assets, Transfers out of Level 3	(12,087)	(12,614)
Assets, Ending Balance	14,915	24,911
Investments [Member] | Consumer loans and asset-backed securities backed by consumer loans [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	135,258	107,157
Assets, Accreted Discounts/Amortized Premiums	(29,320)	(13,754)
Assets, Realized Gain (Loss)	8,415	855
Assets, Change In Net Unrealized Gain/(Loss)	(1,092)	(171)
Assets, Purchases	228,354	129,525
Assets, Sales	(134,854)	(88,354)
Assets, Transfers into Level 3	0	0
Assets, Transfers out of Level 3	0	0
Assets, Ending Balance	206,761	135,258
Investments [Member] | Corporate Debt [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	23,947	25,004
Assets, Accreted Discounts/Amortized Premiums	56	252
Assets, Realized Gain (Loss)	241	527
Assets, Change In Net Unrealized Gain/(Loss)	(964)	223
Assets, Purchases	7,665	97,466
Assets, Sales	(17,688)	(99,525)
Assets, Transfers into Level 3	0	0
Assets, Transfers out of Level 3	(6,939)	0
Assets, Ending Balance	6,318	23,947
Investments [Member] | Secured Notes [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	0
Assets, Accreted Discounts/Amortized Premiums	870
Assets, Realized Gain (Loss)	0
Assets, Change In Net Unrealized Gain/(Loss)	(1,221)
Assets, Purchases	11,268
Assets, Sales	0
Assets, Transfers into Level 3	0
Assets, Transfers out of Level 3	0
Assets, Ending Balance	10,917	0
Investments [Member] | Real Estate Owned [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	26,277	3,349
Assets, Accreted Discounts/Amortized Premiums	0	0
Assets, Realized Gain (Loss)	(653)	411
Assets, Change In Net Unrealized Gain/(Loss)	(1,003)	322
Assets, Purchases	12,793	25,516
Assets, Sales	(2,914)	(3,321)
Assets, Transfers into Level 3	0	0
Assets, Transfers out of Level 3	0	0
Assets, Ending Balance	34,500	26,277
Investments [Member] | Corporate Equity Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	37,465	29,392
Assets, Accreted Discounts/Amortized Premiums	0	0
Assets, Realized Gain (Loss)	1,671	2,347
Assets, Change In Net Unrealized Gain/(Loss)	8,299	(512)
Assets, Purchases	12,708	16,417
Assets, Sales	(16,350)	(10,179)
Assets, Transfers into Level 3	0	0
Assets, Transfers out of Level 3	0	0
Assets, Ending Balance	43,793	37,465
Financial Derivatives - Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	3,140	5,587
Assets, Accreted Discounts/Amortized Premiums	0	0
Assets, Realized Gain (Loss)	(687)	394
Assets, Change In Net Unrealized Gain/(Loss)	715	(1,363)
Assets, Purchases	102	138
Assets, Sales	(1,798)	(1,616)
Assets, Transfers into Level 3	0	0
Assets, Transfers out of Level 3	0	0
Assets, Ending Balance	1,472	3,140
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(600)	(1,200)
Financial Derivatives - Assets [Member] | Total Return Swaps [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	0	155
Assets, Accreted Discounts/Amortized Premiums		0
Assets, Realized Gain (Loss)		224
Assets, Change In Net Unrealized Gain/(Loss)		(155)
Assets, Purchases		1
Assets, Sales		(225)
Assets, Transfers into Level 3		0
Assets, Transfers out of Level 3		0
Assets, Ending Balance		0
Financial Derivatives - Assets [Member] | Warrant [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	0	106
Assets, Accreted Discounts/Amortized Premiums		0
Assets, Realized Gain (Loss)		(100)
Assets, Change In Net Unrealized Gain/(Loss)		(6)
Assets, Purchases		0
Assets, Sales		0
Assets, Transfers into Level 3		0
Assets, Transfers out of Level 3		0
Assets, Ending Balance		0
Financial Derivatives - Assets [Member] | Credit Default Swaps On Asset Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	3,140	5,326
Assets, Accreted Discounts/Amortized Premiums	0	0
Assets, Realized Gain (Loss)	(687)	270
Assets, Change In Net Unrealized Gain/(Loss)	715	(1,202)
Assets, Purchases	102	137
Assets, Sales	(1,798)	(1,391)
Assets, Transfers into Level 3	0	0
Assets, Transfers out of Level 3	0	0
Assets, Ending Balance	$ 1,472	$ 3,140