Financial Derivatives (TBAs) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Financial derivatives–assets, at fair value-	$ 15,479	$ 16,788	$ 20,001
Derivative Liability	24,553	27,621	$ 20,806
Derivative Assets (Liabilities), at Fair Value, Net	(9,074)	(10,833)
TBA securities
Derivative [Line Items]
Notional Amount	(354,077)	(1,053,630)
Derivative, Cost Basis	(380,791)	(1,098,063)
Market Value Underlying	(380,754)	(1,098,479)
Derivative Assets (Liabilities), at Fair Value, Net	37	(416)
TBA securities | Long
Derivative [Line Items]
Notional Amount	(149,990)	(40,100)
Derivative, Cost Basis	155,008	40,585
Market Value Underlying	155,969	40,675
Derivative Assets (Liabilities), at Fair Value, Net	961	90
TBA securities | Short
Derivative [Line Items]
Notional Amount	(504,067)	(1,093,730)
Derivative, Cost Basis	(535,799)	(1,138,648)
Market Value Underlying	(536,723)	(1,139,154)
Derivative Assets (Liabilities), at Fair Value, Net	(924)	(506)
Financial Derivatives - Assets | TBA securities | Long
Derivative [Line Items]
Notional Amount	(149,990)	(40,100)
Derivative, Cost Basis	155,008	40,585
Market Value Underlying	155,969	40,675
Financial derivatives–assets, at fair value-	961	90
Financial Derivatives - Assets | TBA securities | Short
Derivative [Line Items]
Notional Amount	(4,400)	(319,981)
Derivative, Cost Basis	(4,765)	(332,080)
Market Value Underlying	(4,764)	(331,574)
Financial derivatives–assets, at fair value-	1	506
Financial Derivatives - Liabilities | TBA securities | Long
Derivative [Line Items]
Notional Amount	0	0
Derivative, Cost Basis	0	0
Market Value Underlying	0	0
Derivative Liability	0	0
Financial Derivatives - Liabilities | TBA securities | Short
Derivative [Line Items]
Notional Amount	(499,667)	(773,749)
Derivative, Cost Basis	(531,034)	(806,568)
Market Value Underlying	(531,959)	(807,580)
Derivative Liability	$ (925)	$ (1,012)