Financial Derivatives (Schedule of Financial Derivatives) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	$ 23,082	$ 15,479
Financial derivatives–liabilities, at fair value-	(19,438)	(24,553)
Total	3,644	(9,074)
TBA Securities, Purchase Contracts [Member]
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	1	961
Financial derivatives–liabilities, at fair value-	(3,915)	0
TBA Securities, Sale Contracts [Member]
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	3,408	1
Financial derivatives–liabilities, at fair value-	(161)	(925)
Interest rate swaps | Short
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	5,331	125
Financial derivatives–liabilities, at fair value-	(7,856)	(15,109)
Interest rate swaps | Long
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	5,372	8,394
Financial derivatives–liabilities, at fair value-	(1,028)	(65)
Credit default swaps on asset-backed securities
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	320	347
Credit default swaps on asset-backed indices
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	2,087	2,184
Financial derivatives–liabilities, at fair value-	(127)	(130)
Credit default swaps on corporate bonds
Derivatives, Fair Value [Line Items]
Financial derivatives–liabilities, at fair value-	(682)	(747)
Credit default swaps on corporate bond indices
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	3,427	3,420
Financial derivatives–liabilities, at fair value-	(5,128)	(6,438)
Total return swaps
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	2	9
Financial derivatives–liabilities, at fair value-	(338)	(484)
Futures
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	2,704	2
Financial derivatives–liabilities, at fair value-	(163)	(376)
Futures | Short
Derivatives, Fair Value [Line Items]
Total	2,541	(374)
Forwards
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	388	0
Financial derivatives–liabilities, at fair value-	(40)	(279)
Warrants
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	$ 42	$ 36