Financial Derivatives (Schedule of Financial Derivatives) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	$ 15,976	$ 15,479
Financial derivatives–liabilities, at fair value-	(14,119)	(24,553)
Total	1,857	(9,074)
TBA Securities, Purchase Contracts [Member]
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	0	961
Financial derivatives–liabilities, at fair value-	(2,596)	0
TBA Securities, Sale Contracts [Member]
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	2,399	1
Financial derivatives–liabilities, at fair value-	(485)	(925)
Interest rate swaps | Short
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	4,450	125
Financial derivatives–liabilities, at fair value-	(8,094)	(15,109)
Interest rate swaps | Long
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	4,167	8,394
Financial derivatives–liabilities, at fair value-	(757)	(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-	1,599	2,184
Financial derivatives–liabilities, at fair value-	(38)	(130)
Credit default swaps on corporate bonds
Derivatives, Fair Value [Line Items]
Financial derivatives–liabilities, at fair value-	(101)	(747)
Credit default swaps on corporate bond indices
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	174	3,420
Financial derivatives–liabilities, at fair value-	(1,955)	(6,438)
Total return swaps
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	0	9
Financial derivatives–liabilities, at fair value-	0	(484)
Futures
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	1,440	2
Financial derivatives–liabilities, at fair value-	(93)	(376)
Futures | Short
Derivatives, Fair Value [Line Items]
Total	1,347	(374)
Forwards
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	360	0
Financial derivatives–liabilities, at fair value-	0	(279)
Warrants
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	938	36
Put Option [Member]
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	$ 146	$ 0