Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
	Aug. 02, 2022	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Dividends declared (in dollars per share)		$ 0.53	$ 0.52	$ 1.06	$ 1.04
Schedule of Accumulated Other Income (Loss) [Abstract]
Balance, Beginning of Period				$ 72,371	$ 335,868
Net change in unrealized gain (loss)		$ (242,536)	$ 8,480	(881,577)	(141,651)
Transfer of net unrealized loss from AFS to investment securities				0
Reclassification Adjustments Included in Earnings [Abstract]
Interest revenues, Investment securities		2,455	0	2,455	0
Gain on available for sale securities, net		(1,188)	(1,430)	(2,125)	(1,897)
Other comprehensive income, before income taxes		(241,269)	7,050	(881,247)	(143,548)
Federal and state income taxes		(56,467)	1,691	(206,248)	(34,448)
Other comprehensive income, net of income taxes		(184,802)	5,359	(674,999)	(109,100)
Balance, End of Period		(602,628)	226,768	(602,628)	226,768
Accumulated Net Unrealized Gain (Loss) on Available for Sale Securities [Member]
Schedule of Accumulated Other Income (Loss) [Abstract]
Balance, Beginning of Period				69,775	335,032
Net change in unrealized gain (loss)				(881,577)	(141,651)
Transfer of net unrealized loss from AFS to investment securities				267,509
Reclassification Adjustments Included in Earnings [Abstract]
Interest revenues, Investment securities				0
Gain on available for sale securities, net				(2,125)	(1,897)
Other comprehensive income, before income taxes				(616,193)	(143,548)
Federal and state income taxes				(144,215)	(34,448)
Other comprehensive income, net of income taxes				(471,978)	(109,100)
Balance, End of Period		(402,203)	225,932	(402,203)	225,932
Accumulated Unrealized Gain (Loss) on Employee Benefit Plans [Member]
Schedule of Accumulated Other Income (Loss) [Abstract]
Balance, Beginning of Period				2,596	836
Net change in unrealized gain (loss)				0	0
Transfer of net unrealized loss from AFS to investment securities				0
Reclassification Adjustments Included in Earnings [Abstract]
Interest revenues, Investment securities				0
Gain on available for sale securities, net				0	0
Other comprehensive income, before income taxes				0	0
Federal and state income taxes				0	0
Other comprehensive income, net of income taxes				0	0
Balance, End of Period		2,596	836	2,596	836
AOCI, Accumulated Gain (Loss), Debt Securities, Investment Securities Transferred from Available-for-sale, Parent
Schedule of Accumulated Other Income (Loss) [Abstract]
Balance, Beginning of Period				0	0
Net change in unrealized gain (loss)				0	0
Transfer of net unrealized loss from AFS to investment securities				(267,509)
Reclassification Adjustments Included in Earnings [Abstract]
Interest revenues, Investment securities				2,455
Gain on available for sale securities, net				0	0
Other comprehensive income, before income taxes				(265,054)	0
Federal and state income taxes				(62,033)	0
Other comprehensive income, net of income taxes				(203,021)	0
Balance, End of Period		$ (203,021)	$ 0	$ (203,021)	$ 0
Subsequent Event [Member]
Dividends Payable, Date Declared	Aug. 02, 2022
Dividends declared (in dollars per share)	$ 0.53
Dividends Payable, Date to be Paid	Aug. 25, 2022
Dividends Payable, Date of Record	Aug. 16, 2022