Financial Derivatives (TBAs) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Derivative [Line Items]
Financial derivatives–assets, at fair value-	$ 27,864	$ 16,788
Derivative Liability	34,814	27,621
Derivative Assets (Liabilities), at Fair Value, Net	(6,950)	(10,833)
TBA securities
Derivative [Line Items]
Notional Amount	(319,677)	(1,053,630)
Derivative, Cost Basis	(344,166)	(1,098,063)
Market Value Underlying	(343,302)	(1,098,479)
Derivative Assets (Liabilities), at Fair Value, Net	864	(416)
TBA securities | Long
Derivative [Line Items]
Notional Amount	(168,890)	(40,100)
Derivative, Cost Basis	175,252	40,585
Market Value Underlying	175,490	40,675
Derivative Assets (Liabilities), at Fair Value, Net	238	90
TBA securities | Short
Derivative [Line Items]
Notional Amount	(488,567)	(1,093,730)
Derivative, Cost Basis	(519,418)	(1,138,648)
Market Value Underlying	(518,792)	(1,139,154)
Derivative Assets (Liabilities), at Fair Value, Net	626	(506)
Financial Derivatives - Assets | TBA securities | Long
Derivative [Line Items]
Notional Amount	(100,890)	(40,100)
Derivative, Cost Basis	103,882	40,585
Market Value Underlying	104,276	40,675
Financial derivatives–assets, at fair value-	394	90
Financial Derivatives - Assets | TBA securities | Short
Derivative [Line Items]
Notional Amount	(401,722)	(319,981)
Derivative, Cost Basis	(428,049)	(332,080)
Market Value Underlying	(427,293)	(331,574)
Financial derivatives–assets, at fair value-	756	506
Financial Derivatives - Liabilities | TBA securities | Long
Derivative [Line Items]
Notional Amount	68,000	0
Derivative, Cost Basis	71,370	0
Market Value Underlying	71,214	0
Derivative Liability	(156)	0
Financial Derivatives - Liabilities | TBA securities | Short
Derivative [Line Items]
Notional Amount	(86,845)	(773,749)
Derivative, Cost Basis	(91,369)	(806,568)
Market Value Underlying	(91,499)	(807,580)
Derivative Liability	$ (130)	$ (1,012)