Financial Derivatives (Schedule of Gains and Losses on Derivative Contracts) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Derivative [Line Items]
Net Realized Gains (Losses) on Periodic Settlements of Interest Rate Swaps	$ 7,462	$ 2,841	$ 22,489	$ 640
Net Realized Gains (Losses) Other Than Periodic Settlements of Interest Rate Swaps	18,821	16,154	8,128	88,468
Realized gains (losses) on financial derivatives, net	26,283	18,995	30,617	89,108
Change in Net Unrealized Gains (Losses) on Accrued Periodic Settlements of Interest Rate Swaps	6,656	361	13,421	1,759
Change in Net Unrealized Gains (Losses) Other Than on Accrued Periodic Settlements of Interest Rate Swaps	49,129	49,880	53,473	96,280
Unrealized gains (losses) on financial derivatives, net	55,785	50,241	66,894	98,039
Derivative [Member]
Derivative [Line Items]
Foreign currency translation	(9)	(18)	(3)	(43)
Interest rate swaps | Interest Rate Risk [Member]
Derivative [Line Items]
Net Realized Gains (Losses) on Periodic Settlements of Interest Rate Swaps	7,462	2,841	22,489	640
Net Realized Gains (Losses) Other Than Periodic Settlements of Interest Rate Swaps	3,405	5,442	(5,729)	15,514
Realized gains (losses) on financial derivatives, net	10,867	8,283	16,760	16,154
Change in Net Unrealized Gains (Losses) on Accrued Periodic Settlements of Interest Rate Swaps	6,656	361	13,421	1,759
Change in Net Unrealized Gains (Losses) Other Than on Accrued Periodic Settlements of Interest Rate Swaps	38,828	22,845	44,706	62,879
Unrealized gains (losses) on financial derivatives, net	45,484	23,206	58,127	64,638
Credit default swaps on asset-backed securities | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gains (Losses) Other Than Periodic Settlements of Interest Rate Swaps		(844)		(854)
Realized gains (losses) on financial derivatives, net		(844)		(854)
Change in Net Unrealized Gains (Losses) Other Than on Accrued Periodic Settlements of Interest Rate Swaps		717		615
Unrealized gains (losses) on financial derivatives, net		717		615
Credit default swaps on corporate bond indices | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gains (Losses) Other Than Periodic Settlements of Interest Rate Swaps	(975)	375	(1,215)	40
Realized gains (losses) on financial derivatives, net	(975)	375	(1,215)	40
Change in Net Unrealized Gains (Losses) Other Than on Accrued Periodic Settlements of Interest Rate Swaps	224	(514)	2,156	1,190
Unrealized gains (losses) on financial derivatives, net	224	(514)	2,156	1,190
Credit default swaps on corporate bond indices | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gains (Losses) Other Than Periodic Settlements of Interest Rate Swaps	(3,982)	811	(6,071)	1,048
Realized gains (losses) on financial derivatives, net	(3,982)	811	(6,071)	1,048
Change in Net Unrealized Gains (Losses) Other Than on Accrued Periodic Settlements of Interest Rate Swaps	3,531	(1,281)	2,565	2,376
Unrealized gains (losses) on financial derivatives, net	3,531	(1,281)	2,565	2,376
Credit default swaps on corporate bonds | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gains (Losses) Other Than Periodic Settlements of Interest Rate Swaps	(42)	(57)	(124)	(76)
Realized gains (losses) on financial derivatives, net	(42)	(57)	(124)	(76)
Change in Net Unrealized Gains (Losses) Other Than on Accrued Periodic Settlements of Interest Rate Swaps	15	(18)	(9)	89
Unrealized gains (losses) on financial derivatives, net	15	(18)	(9)	89
Total return swaps | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gains (Losses) Other Than Periodic Settlements of Interest Rate Swaps		0		0
Realized gains (losses) on financial derivatives, net		0		0
Change in Net Unrealized Gains (Losses) Other Than on Accrued Periodic Settlements of Interest Rate Swaps		(37)		(37)
Unrealized gains (losses) on financial derivatives, net		(37)		(37)
Total return swaps | Equity Market/Credit Risk [Member]
Derivative [Line Items]
Net Realized Gains (Losses) Other Than Periodic Settlements of Interest Rate Swaps	30		30
Realized gains (losses) on financial derivatives, net	30		30
Change in Net Unrealized Gains (Losses) Other Than on Accrued Periodic Settlements of Interest Rate Swaps	16		16
Unrealized gains (losses) on financial derivatives, net	16		16
TBA securities | Interest Rate Risk [Member]
Derivative [Line Items]
Net Realized Gains (Losses) Other Than Periodic Settlements of Interest Rate Swaps	13,015	9,085	17,287	55,876
Realized gains (losses) on financial derivatives, net	13,015	9,085	17,287	55,876
Change in Net Unrealized Gains (Losses) Other Than on Accrued Periodic Settlements of Interest Rate Swaps	3,786	27,926	165	27,997
Unrealized gains (losses) on financial derivatives, net	3,786	27,926	165	27,997
Futures | Interest Rate Risk [Member]
Derivative [Line Items]
Net Realized Gains (Losses) Other Than Periodic Settlements of Interest Rate Swaps		445		15,493
Realized gains (losses) on financial derivatives, net		445		15,493
Change in Net Unrealized Gains (Losses) Other Than on Accrued Periodic Settlements of Interest Rate Swaps		365		183
Unrealized gains (losses) on financial derivatives, net		365		183
Futures | Interest Rate/Currency Risk [Member]
Derivative [Line Items]
Net Realized Gains (Losses) Other Than Periodic Settlements of Interest Rate Swaps	7,253		4,189
Realized gains (losses) on financial derivatives, net	7,253		4,189
Change in Net Unrealized Gains (Losses) Other Than on Accrued Periodic Settlements of Interest Rate Swaps	2,214		3,326
Unrealized gains (losses) on financial derivatives, net	2,214		3,326
Forwards | Currency risk [Member]
Derivative [Line Items]
Net Realized Gains (Losses) Other Than Periodic Settlements of Interest Rate Swaps	429	897	73	1,693
Realized gains (losses) on financial derivatives, net	429	897	73	1,693
Change in Net Unrealized Gains (Losses) Other Than on Accrued Periodic Settlements of Interest Rate Swaps	203	17	167	468
Unrealized gains (losses) on financial derivatives, net	203	17	167	468
Warrants | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gains (Losses) Other Than Periodic Settlements of Interest Rate Swaps	(312)		(312)
Realized gains (losses) on financial derivatives, net	(312)		(312)
Change in Net Unrealized Gains (Losses) Other Than on Accrued Periodic Settlements of Interest Rate Swaps	312		381
Unrealized gains (losses) on financial derivatives, net	$ 312		$ 381
Warrants | Equity Market/Credit Risk [Member]
Derivative [Line Items]
Net Realized Gains (Losses) Other Than Periodic Settlements of Interest Rate Swaps		0		(413)
Realized gains (losses) on financial derivatives, net		0		(413)
Change in Net Unrealized Gains (Losses) Other Than on Accrued Periodic Settlements of Interest Rate Swaps		(140)		372
Unrealized gains (losses) on financial derivatives, net		$ (140)		372
Options | Credit Risk [Member]
Derivative [Line Items]
Net Realized Gains (Losses) Other Than Periodic Settlements of Interest Rate Swaps				147
Realized gains (losses) on financial derivatives, net				147
Change in Net Unrealized Gains (Losses) Other Than on Accrued Periodic Settlements of Interest Rate Swaps				148
Unrealized gains (losses) on financial derivatives, net				$ 148