Derivative Instruments - Volume of Activity, in terms of Notional Amount, Related to Derivative Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Derivative [Line Items]
Beginning of Period		$ 100,000
Additions	$ 430,000	450,000	$ 755,000	$ 1,365,000
Scheduled Settlements	275,000	550,000	600,000	1,365,000
End of Period	155,000		155,000
Interest Rate Swap
Derivative [Line Items]
Beginning of Period	175,000	675,000	150,000	275,000
Additions	75,000		145,000	450,000
Early Terminations	(20,000)	(150,000)	(65,000)	(200,000)
End of Period	230,000	525,000	230,000	525,000
2-year U.S. Treasury Note Futures
Derivative [Line Items]
Additions				50,000
Scheduled Settlements				(50,000)
10-year U.S. Treasury Note Futures
Derivative [Line Items]
Beginning of Period			25,000
Additions		165,000	50,000	540,100
Scheduled Settlements		(120,000)	(50,000)	(320,000)
Early Terminations			(25,000)	(175,100)
End of Period	$ 0	45,000	0	45,000
Purchased Call Options on Ten Year U.S. Treasury Note Futures
Derivative [Line Items]
Beginning of Period		65,200	25,000
Additions				65,200
Scheduled Settlements		$ (65,200)	$ (25,000)	$ (65,200)