Valuation (Fair Value Measurement Using Significant Unobservable Inputs) (Details) - Level 3 [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	$ 493,541	$ 638,486	$ 756,934
Assets, Accreted Discounts/Amortized Premiums	(16,102)	(20,675)	13,309
Assets, Realized Gain (Loss)	(1,827)	20,808	47,557
Assets, Change In Net Unrealized Gain/(Loss)	(1,998)	(29,552)	(20,446)
Assets, Purchases	487,837	430,683	782,596
Assets, Sales	(433,484)	(504,371)	(656,716)
Assets, Transfers into Level 3	10,041	6,687	0
Assets, Transfers out of Level 3	(14,171)	(48,525)	(284,748)
Assets, Ending Balance	523,837	493,541	638,486
Liabilities, Begining Balance	(6,159)	(1,013)	(1,333)
Liabilities, Accreted Discounts/Amortized Premiums	(1)	(17)	(15)
Liabilities, Realized Gain/(Loss)	(7,495)	2,611	(78)
Liabilities, Change In Net Unrealized Gain/(Loss)	4,977	(5,201)	89
Liabilities Purchases/Payments	8,853	2,149	246
Liabilities, Sales/Issuance	(680)	(4,688)	78
Liabilities, Transfers into Level 3	0	0	0
Liabilities, Transfers out of Level 3	0	0	0
Liabilities, Ending Balance	(505)	(6,159)	(1,013)
Securitized Debt [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities, Begining Balance	0	(774)	(983)
Liabilities, Accreted Discounts/Amortized Premiums		(15)	(15)
Liabilities, Realized Gain/(Loss)		0	0
Liabilities, Change In Net Unrealized Gain/(Loss)		26	(22)
Liabilities, Payments		763	246
Liabilities, Issuances		0	0
Liabilities, Transfers into Level 3		0	0
Liabilities, Transfers out of Level 3		0	0
Liabilities, Ending Balance		0	(774)
Guarantees [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities, Begining Balance	(828)	0
Liabilities, Accreted Discounts/Amortized Premiums	0	0
Liabilities, Realized Gain/(Loss)	0	0
Liabilities, Change In Net Unrealized Gain/(Loss)	828	(828)
Liabilities, Payments	0	0
Liabilities, Issuances	0	0
Liabilities, Transfers into Level 3	0	0
Liabilities, Transfers out of Level 3	0	0
Liabilities, Ending Balance	0	(828)	0
Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	486,974	626,999	740,288
Assets, Accreted Discounts/Amortized Premiums	(16,102)	(20,675)	13,309
Assets, Realized Gain (Loss)	(5,889)	23,659	52,153
Assets, Change In Net Unrealized Gain/(Loss)	(1,407)	(31,735)	(24,993)
Assets, Purchases	480,146	430,605	782,032
Assets, Sales	(421,342)	(500,041)	(651,042)
Assets, Transfers into Level 3	10,041	6,687	0
Assets, Transfers out of Level 3	(14,171)	(48,525)	(284,748)
Assets, Ending Balance	518,250	486,974	626,999
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(14,700)	(20,700)	6,300
Investments [Member] | Agency residential mortgage-backed securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	24,918	31,385	40,504
Assets, Accreted Discounts/Amortized Premiums	(7,998)	(8,355)	(8,738)
Assets, Realized Gain (Loss)	(536)	223	1,404
Assets, Change In Net Unrealized Gain/(Loss)	845	81	(2,078)
Assets, Purchases	12,665	6,977	8,448
Assets, Sales	(272)	(5,393)	(8,155)
Assets, Transfers into Level 3	0	0	0
Assets, Transfers out of Level 3	0	0	0
Assets, Ending Balance	29,622	24,918	31,385
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	116,435	274,369	580,772
Assets, Accreted Discounts/Amortized Premiums	1,896	8,593	20,544
Assets, Realized Gain (Loss)	(2,748)	20,648	38,600
Assets, Change In Net Unrealized Gain/(Loss)	3,972	(16,429)	(18,406)
Assets, Purchases	30,065	62,994	382,956
Assets, Sales	(55,407)	(191,902)	(445,349)
Assets, Transfers into Level 3	10,041	6,687	0
Assets, Transfers out of Level 3	(14,171)	(48,525)	(284,748)
Assets, Ending Balance	90,083	116,435	274,369
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	34,145	53,311	32,994
Assets, Accreted Discounts/Amortized Premiums	1,627	3,076	1,328
Assets, Realized Gain (Loss)	1,008	2,000	7,055
Assets, Change In Net Unrealized Gain/(Loss)	(6,081)	(4,183)	(357)
Assets, Purchases	24,488	21,382	116,128
Assets, Sales	(11,919)	(41,441)	(103,837)
Assets, Transfers into Level 3	0	0	0
Assets, Transfers out of Level 3	0	0	0
Assets, Ending Balance	43,268	34,145	53,311
Investments [Member] | Commercial Mortgage Loans [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	66,399	28,309	23,887
Assets, Accreted Discounts/Amortized Premiums	2,463	1,895	2,739
Assets, Realized Gain (Loss)	1,920	1,114	3,156
Assets, Change In Net Unrealized Gain/(Loss)	(1,434)	(142)	(632)
Assets, Purchases	39,684	69,778	41,856
Assets, Sales	(47,903)	(34,555)	(42,697)
Assets, Transfers into Level 3	0	0	0
Assets, Transfers out of Level 3	0	0	0
Assets, Ending Balance	61,129	66,399	28,309
Investments [Member] | Residential Mortgage Loans [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	22,089	27,482	24,062
Assets, Accreted Discounts/Amortized Premiums	467	1,363	1,267
Assets, Realized Gain (Loss)	774	2,372	1,424
Assets, Change In Net Unrealized Gain/(Loss)	(800)	(505)	84
Assets, Purchases	102,224	19,555	14,863
Assets, Sales	(40,464)	(28,178)	(14,218)
Assets, Transfers into Level 3	0	0	0
Assets, Transfers out of Level 3	0	0	0
Assets, Ending Balance	84,290	22,089	27,482
Investments [Member] | Collateralized Loan Obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	45,974	121,994	38,069
Assets, Accreted Discounts/Amortized Premiums	(3,829)	(21,110)	(2,577)
Assets, Realized Gain (Loss)	71	46	342
Assets, Change In Net Unrealized Gain/(Loss)	2,471	(4,033)	(1,879)
Assets, Purchases	27,862	59,102	118,607
Assets, Sales	(27,593)	(110,025)	(30,568)
Assets, Transfers into Level 3	0	0	0
Assets, Transfers out of Level 3	0	0	0
Assets, Ending Balance	44,956	45,974	121,994
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	115,376	24,294	0
Assets, Accreted Discounts/Amortized Premiums	(10,668)	(6,197)	(1,184)
Assets, Realized Gain (Loss)	(164)	0	0
Assets, Change In Net Unrealized Gain/(Loss)	(7,818)	283	(530)
Assets, Purchases	174,664	139,373	29,402
Assets, Sales	(156,918)	(42,377)	(3,394)
Assets, Transfers into Level 3	0	0	0
Assets, Transfers out of Level 3	0	0	0
Assets, Ending Balance	114,472	115,376	24,294
Investments [Member] | Corporate Debt [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	27,028	42,708	0
Assets, Accreted Discounts/Amortized Premiums	(60)	60	(70)
Assets, Realized Gain (Loss)	(8,326)	(4,028)	0
Assets, Change In Net Unrealized Gain/(Loss)	6,864	(6,882)	(877)
Assets, Purchases	26,851	28,942	43,808
Assets, Sales	(27,353)	(33,772)	(153)
Assets, Transfers into Level 3	0	0	0
Assets, Transfers out of Level 3	0	0	0
Assets, Ending Balance	25,004	27,028	42,708
Investments [Member] | Real Estate Owned [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	12,522	8,635	0
Assets, Accreted Discounts/Amortized Premiums	0	0	0
Assets, Realized Gain (Loss)	2,256	1,168	172
Assets, Change In Net Unrealized Gain/(Loss)	(458)	381	(113)
Assets, Purchases	17,526	14,155	11,247
Assets, Sales	(28,497)	(11,817)	(2,671)
Assets, Transfers into Level 3	0	0	0
Assets, Transfers out of Level 3	0	0	0
Assets, Ending Balance	3,349	12,522	8,635
Investments [Member] | Private Corporate Equity Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	22,088	14,512	0
Assets, Accreted Discounts/Amortized Premiums	0	0	0
Assets, Realized Gain (Loss)	(144)	116	0
Assets, Change In Net Unrealized Gain/(Loss)	1,032	(306)	(205)
Assets, Purchases	24,117	8,347	14,717
Assets, Sales	(25,016)	(581)	0
Assets, Transfers into Level 3	0	0	0
Assets, Transfers out of Level 3	0	0	0
Assets, Ending Balance	22,077	22,088	14,512
Investments Sold Short [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities, Begining Balance	(448)	0
Liabilities, Accreted Discounts/Amortized Premiums	(1)	(2)
Liabilities, Realized Gain/(Loss)	362	197
Liabilities, Change In Net Unrealized Gain/(Loss)	(228)	228
Liabilities, Purchases	315	1,372
Liabilities, Sales	0	(2,243)
Liabilities, Transfers into Level 3	0	0
Liabilities, Transfers out of Level 3	0	0
Liabilities, Ending Balance	0	(448)	0
Investments Sold Short [Member] | Corporate Debt Sold Short [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities, Begining Balance	(448)	0
Liabilities, Accreted Discounts/Amortized Premiums	(1)	(2)
Liabilities, Realized Gain/(Loss)	362	197
Liabilities, Change In Net Unrealized Gain/(Loss)	(228)	228
Liabilities, Purchases	315	1,372
Liabilities, Sales	0	(2,243)
Liabilities, Transfers into Level 3	0	0
Liabilities, Transfers out of Level 3	0	0
Liabilities, Ending Balance	0	(448)	0
Financial Derivatives - Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	6,567	11,487	16,646
Assets, Accreted Discounts/Amortized Premiums	0	0	0
Assets, Realized Gain (Loss)	4,062	(2,851)	(4,596)
Assets, Change In Net Unrealized Gain/(Loss)	(591)	2,183	4,547
Assets, Purchases	7,691	78	564
Assets, Sales	(12,142)	(4,330)	(5,674)
Assets, Transfers into Level 3	0	0	0
Assets, Transfers out of Level 3	0	0	0
Assets, Ending Balance	5,587	6,567	11,487
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(800)	7	(1,600)
Financial Derivatives - Assets [Member] | Total Return Swaps [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	85	0
Assets, Accreted Discounts/Amortized Premiums	0	0
Assets, Realized Gain (Loss)	3,070	113
Assets, Change In Net Unrealized Gain/(Loss)	70	85
Assets, Purchases	57	0
Assets, Sales	(3,127)	(113)
Assets, Transfers into Level 3	0	0
Assets, Transfers out of Level 3	0	0
Assets, Ending Balance	155	85	0
Financial Derivatives - Assets [Member] | Warrant [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	150	100	0
Assets, Accreted Discounts/Amortized Premiums	0	0	0
Assets, Realized Gain (Loss)	(50)	0	0
Assets, Change In Net Unrealized Gain/(Loss)	6	0	0
Assets, Purchases	7,486	50	100
Assets, Sales	(7,486)	0	0
Assets, Transfers into Level 3	0	0	0
Assets, Transfers out of Level 3	0	0	0
Assets, Ending Balance	106	150	100
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	6,332	11,387	16,646
Assets, Accreted Discounts/Amortized Premiums	0	0	0
Assets, Realized Gain (Loss)	1,042	(2,964)	(4,596)
Assets, Change In Net Unrealized Gain/(Loss)	(667)	2,098	4,547
Assets, Purchases	148	28	464
Assets, Sales	(1,529)	(4,217)	(5,674)
Assets, Transfers into Level 3	0	0	0
Assets, Transfers out of Level 3	0	0	0
Assets, Ending Balance	5,326	6,332	11,387
Financial Derivatives - Liabilities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities, Begining Balance	(4,883)	(239)	(350)
Liabilities, Accreted Discounts/Amortized Premiums	0	0	0
Liabilities, Realized Gain/(Loss)	(7,857)	2,414	(78)
Liabilities, Change In Net Unrealized Gain/(Loss)	4,377	(4,627)	111
Liabilities, Purchases	8,538	14	0
Liabilities, Sales	(680)	(2,445)	78
Liabilities, Transfers into Level 3	0	0	0
Liabilities, Transfers out of Level 3	0	0	0
Liabilities, Ending Balance	(505)	(4,883)	(239)
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(200)	(4,600)	(100)
Financial Derivatives - Liabilities [Member] | Total Return Swaps [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities, Begining Balance	(4,662)	0
Liabilities, Accreted Discounts/Amortized Premiums	0	0
Liabilities, Realized Gain/(Loss)	(7,534)	2,516
Liabilities, Change In Net Unrealized Gain/(Loss)	4,413	(4,662)
Liabilities, Purchases	8,214	14
Liabilities, Sales	(680)	(2,530)
Liabilities, Transfers into Level 3	0	0
Liabilities, Transfers out of Level 3	0	0
Liabilities, Ending Balance	(249)	(4,662)	0
Financial Derivatives - Liabilities [Member] | Credit Default Swaps On Asset Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities, Begining Balance	(221)	(239)	(350)
Liabilities, Accreted Discounts/Amortized Premiums	0	0	0
Liabilities, Realized Gain/(Loss)	(323)	(102)	(78)
Liabilities, Change In Net Unrealized Gain/(Loss)	(36)	35	111
Liabilities, Purchases	324	0	0
Liabilities, Sales	0	85	78
Liabilities, Transfers into Level 3	0	0	0
Liabilities, Transfers out of Level 3	0	0	0
Liabilities, Ending Balance	$ (256)	(221)	(239)
Guarantees [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)		$ (800)
Securitized Debt [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)			$ (22)