Financial Derivatives (Schedule of Financial Derivatives) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	$ 16,788	$ 20,001
Financial derivatives–liabilities, at fair value-	(27,621)	$ (20,806)
Total	(10,833)
TBA Securities, Purchase Contracts [Member]
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	90
TBA Securities, Sale Contracts [Member]
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	506
Financial derivatives–liabilities, at fair value-	(1,012)
Interest rate swaps | Short
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	3,914
Financial derivatives–liabilities, at fair value-	(8,513)
Interest rate swaps | Long
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	1,554
Financial derivatives–liabilities, at fair value-	(206)
Credit default swaps on asset-backed securities
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	993
Credit default swaps on asset-backed indices
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	3,319
Financial derivatives–liabilities, at fair value-	(250)
Credit default swaps on corporate bonds
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	2
Financial derivatives–liabilities, at fair value-	(1,693)
Credit default swaps on corporate bond indices
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	5,599
Financial derivatives–liabilities, at fair value-	(14,524)
Total return swaps
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	620
Financial derivatives–liabilities, at fair value-	(1,209)
Futures
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	148
Financial derivatives–liabilities, at fair value-	(45)
Futures | Short
Derivatives, Fair Value [Line Items]
Total	103
Forwards
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	43
Financial derivatives–liabilities, at fair value-	$ (169)