Financial Derivatives (Schedule of Financial Derivatives) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	$ 31,752	$ 16,788
Financial derivatives–liabilities, at fair value-	(47,772)	(27,621)
Total	(16,020)	(10,833)
TBA Securities, Purchase Contracts [Member]
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	302	90
TBA Securities, Sale Contracts [Member]
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	249	506
Financial derivatives–liabilities, at fair value-	(6,391)	(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-	(31,959)	(8,513)
Interest rate swaps | Long
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	8,592	1,554
Financial derivatives–liabilities, at fair value-	(327)	(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-	14,276	3,319
Financial derivatives–liabilities, at fair value-	(162)	(250)
Credit default swaps on corporate bonds
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	1,202	2
Financial derivatives–liabilities, at fair value-	(62)	(1,693)
Credit default swaps on corporate bond indices
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	3,732	5,599
Financial derivatives–liabilities, at fair value-	(1,922)	(14,524)
Total return swaps
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	37	620
Financial derivatives–liabilities, at fair value-	(839)	(1,209)
Options
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	2,658	0
Futures
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	37	148
Financial derivatives–liabilities, at fair value-	(6,049)	(45)
Futures | Short
Derivatives, Fair Value [Line Items]
Total	(6,012)	103
Forwards
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	188	43
Financial derivatives–liabilities, at fair value-	(61)	(169)
Warrants
Derivatives, Fair Value [Line Items]
Financial derivatives–assets, at fair value-	$ 126	$ 0