Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
	Aug. 01, 2023	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Dividends declared (in dollars per share)		$ 0.54	$ 0.53	$ 1.08	$ 1.06
Schedule of Accumulated Other Income (Loss) [Abstract]
Balance, Beginning of Period				$ (836,955)	$ 72,371
Net change in unrealized gain (loss)		$ (160,408)	$ (242,536)	(36,363)	(881,577)
Transfer of net unrealized loss from AFS to investment securities					0
Interest revenue, Investment securities		16,033	2,455	32,084	2,455
Loss (gain) on available for sale securities, net		3,010	(1,188)	3,010	(2,125)
Other comprehensive income, before income taxes		(141,365)	(241,269)	(1,269)	(881,247)
Federal and state income taxes		(33,247)	(56,467)	(1,552)	(206,248)
Other comprehensive income, net of income taxes		(108,118)	(184,802)	283	(674,999)
Balance, End of Period		(836,672)	(602,628)	(836,672)	(602,628)
Accumulated Net Unrealized Gain (Loss) on Available for Sale Securities [Member]
Schedule of Accumulated Other Income (Loss) [Abstract]
Balance, Beginning of Period				(664,618)	69,775
Net change in unrealized gain (loss)				(36,363)	(881,577)
Transfer of net unrealized loss from AFS to investment securities					267,509
Interest revenue, Investment securities				0	0
Loss (gain) on available for sale securities, net				3,010	(2,125)
Other comprehensive income, before income taxes				(33,353)	(616,193)
Federal and state income taxes				(8,839)	(144,215)
Other comprehensive income, net of income taxes				(24,514)	(471,978)
Balance, End of Period		(689,132)	(402,203)	(689,132)	(402,203)
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				(172,337)	0
Net change in unrealized gain (loss)				0	0
Transfer of net unrealized loss from AFS to investment securities					(267,509)
Interest revenue, Investment securities				32,084	2,455
Loss (gain) on available for sale securities, net				0	0
Other comprehensive income, before income taxes				32,084	(265,054)
Federal and state income taxes				7,287	(62,033)
Other comprehensive income, net of income taxes				24,797	(203,021)
Balance, End of Period		(147,540)	(203,021)	(147,540)	(203,021)
Accumulated Unrealized Gain (Loss) on Employee Benefit Plans [Member]
Schedule of Accumulated Other Income (Loss) [Abstract]
Balance, Beginning of Period				0	2,596
Net change in unrealized gain (loss)				0	0
Transfer of net unrealized loss from AFS to investment securities					0
Interest revenue, Investment securities				0	0
Loss (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		$ 0	$ 2,596	$ 0	$ 2,596
Subsequent Event [Member]
Dividends Payable, Date Declared	Aug. 01, 2023
Dividends declared (in dollars per share)	$ 0.54
Dividends Payable, Date to be Paid	Aug. 30, 2023
Dividends Payable, Date of Record	Aug. 15, 2023