Derivative and Other Hedging Instruments (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($) month	Dec. 31, 2021 USD ($) month	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Interest Rate Swaption [Member]
Average Maturity (Years)	9 years 9 months 18 days	9 years 7 months 6 days
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration | month	13	18
Notional Amount	$ 3,050,000	$ 13,000,000
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	857,000	23,000	$ (156,000)
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	1,750,000	8,050,000	7,000,000
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	$ (11,700,000)	$ (5,450,000)	(5,450,000)
Derivative, Average Fixed Interest Rate	2.32%	1.93%
Interest Rate Derivatives, at Fair Value, Net	$ 293,000	$ 290,000
Options At Cost	65,000	328,000
TBA and Forward Settling Agency Securities [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(2,860,000)	(552,000)	1,497,000
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	312,307,000	352,658,000	286,586,000
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period		(356,349,000)	(263,544,000)
Derivative Asset, Fair Value, Gross Asset	18,574,000	27,140,000
Derivative, Fair Value, Net	167,000	(44,000)
US Treasury Securities [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	811,000	42,000	(106,000)
Derivative, Fair Value, Net	56,000	(15,000)
Credit Default Swap
Derivative, Fair Value, Net	(2,000)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	4,679,000	1,054,000	(2,334,000)
Derivative assets, at fair value	617,000	317,000
At Carrying Value
Credit Default Swaps	0
Short [Member] | US Treasury Securities [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	1,482,000	444,000	(905,000)
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	15,548,000	12,691,000	18,912,000
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	17,765,000	(14,388,000)	(16,849,000)
Derivative Asset, Fair Value, Gross Asset	10,505,000	1,957,000
Long [Member] | US Treasury Securities [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(32,000)	(25,000)	102,000
Trading Securities Added During the Period	10,202,000	7,618,000	7,011,000
Notional Amount Of Trading Securities Settlement Expiration During The Period	(10,317,000)	(7,146,000)	(7,106,000)
Debt Securities, Trading, and Equity Securities, FV-NI	$ 357,000	$ 472,000	$ 0	$ 95,000