Financial Derivatives (Schedule of Financial Derivatives) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	$ 13,028	$ 15,479
Financial derivatives–liabilities, at fair value-	(14,171)	(24,553)
Total	(1,143)	(9,074)
TBA Securities, Purchase Contracts [Member]
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	410	961
Financial derivatives–liabilities, at fair value-	(4)	0
TBA Securities, Sale Contracts [Member]
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	1,618	1
Financial derivatives–liabilities, at fair value-	(325)	(925)
Interest rate swaps | Short
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	2,060	125
Financial derivatives–liabilities, at fair value-	(10,037)	(15,109)
Interest rate swaps | Long
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	5,160	8,394
Financial derivatives–liabilities, at fair value-	(503)	(65)
Credit default swaps on asset-backed securities
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	303	347
Credit default swaps on asset-backed indices
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	1,357	2,184
Financial derivatives–liabilities, at fair value-	(91)	(130)
Credit default swaps on corporate bonds
Derivatives, Fair Value [Line Items]
Financial derivatives–liabilities, at fair value-	(384)	(747)
Credit default swaps on corporate bond indices
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	200	3,420
Financial derivatives–liabilities, at fair value-	(2,616)	(6,438)
Total return swaps
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	520	9
Financial derivatives–liabilities, at fair value-	(56)	(484)
Futures
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	659	2
Financial derivatives–liabilities, at fair value-	(155)	(376)
Futures | Short
Derivatives, Fair Value [Line Items]
Total	504	(374)
Forwards
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	445	0
Financial derivatives–liabilities, at fair value-	0	(279)
Warrants
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	2	36
Put Option [Member]
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	$ 294	$ 0