Financial Derivatives (Schedule of Financial Derivatives) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	$ 27,186	$ 16,788
Financial derivatives–liabilities, at fair value-	(34,863)	(27,621)
Total	(7,677)	(10,833)
TBA Securities, Purchase Contracts [Member]
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	502	90
TBA Securities, Sale Contracts [Member]
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	1,264	506
Financial derivatives–liabilities, at fair value-	(158)	(1,012)
Interest rate swaps | Short
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	0	3,914
Financial derivatives–liabilities, at fair value-	(32,684)	(8,513)
Interest rate swaps | Long
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	15,087	1,554
Financial derivatives–liabilities, at fair value-	(8)	(206)
Credit default swaps on asset-backed securities
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	353	993
Credit default swaps on asset-backed indices
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	7,790	3,319
Financial derivatives–liabilities, at fair value-	(152)	(250)
Credit default swaps on corporate bonds
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	0	2
Financial derivatives–liabilities, at fair value-	(56)	(1,693)
Credit default swaps on corporate bond indices
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	1,535	5,599
Financial derivatives–liabilities, at fair value-	(1,346)	(14,524)
Total return swaps
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	442	620
Financial derivatives–liabilities, at fair value-	(77)	(1,209)
Futures
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	0	148
Financial derivatives–liabilities, at fair value-	(382)	(45)
Futures | Short
Derivatives, Fair Value [Line Items]
Total	(382)	103
Forwards
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	182	43
Financial derivatives–liabilities, at fair value-	0	(169)
Warrants
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	$ 31	$ 0