Derivative Instruments, Realized Gain (Loss) Related to Derivatives (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Realized gain (loss) on derivatives, net	$ (10,139)	$ 4,558	$ (14,880)	$ (14,198)
Not Designated as Hedging Instrument [Member]
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Realized gain (loss) on derivatives, net	(10,139)	4,558	(14,880)	(14,198)
Not Designated as Hedging Instrument [Member] | Realized Gain (Loss) on Derivatives, Net [Member] | Interest Rate Swaps [Member]
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Realized gain (loss) on derivatives, net	(209)	(6,759)	(292)	(54,624)
Not Designated as Hedging Instrument [Member] | Realized Gain (Loss) on Derivatives, Net [Member] | Swaptions [Member]
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Realized gain (loss) on derivatives, net	(321)	(212)	(594)	(212)
Not Designated as Hedging Instrument [Member] | Realized Gain (Loss) on Derivatives, Net [Member] | TBAs [Member]
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Realized gain (loss) on derivatives, net	(7,473)	(115)	(10,739)	344
Not Designated as Hedging Instrument [Member] | Realized Gain (Loss) on Derivatives, Net [Member] | Treasury Futures [Member]
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Realized gain (loss) on derivatives, net	$ (2,136)	$ 11,644	$ (3,255)	$ 40,294