Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
	Nov. 01, 2022	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Dividends declared (in dollars per share)		$ 0.53	$ 0.52	$ 1.59	$ 1.56
Schedule of Accumulated Other Income (Loss) [Abstract]
Balance, Beginning of Period				$ 72,371	$ 335,868
Net change in unrealized gain (loss)		$ (412,084)	$ (74,525)	(1,293,661)	(216,176)
Transfer of net unrealized loss from AFS to investment securities				0
Reclassification Adjustments Included in Earnings [Abstract]
Interest revenue, Investment securities		21,675	0	24,130	0
Operating expense, Personnel		(3,483)	0	(3,483)	0
Gain on available for sale securities, net		(892)	(1,255)	(3,017)	(3,152)
Other comprehensive income, before income taxes		(394,784)	(75,780)	(1,276,031)	(219,328)
Federal and state income taxes		(92,467)	(18,184)	(298,715)	(52,632)
Other comprehensive income, net of income taxes		(302,317)	(57,596)	(977,316)	(166,696)
Balance, End of Period		(904,945)	169,172	(904,945)	169,172
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)				(1,293,661)	(216,176)
Transfer of net unrealized loss from AFS to investment securities				267,509
Reclassification Adjustments Included in Earnings [Abstract]
Interest revenue, Investment securities				0
Operating expense, Personnel				0
Gain on available for sale securities, net				(3,017)	(3,152)
Other comprehensive income, before income taxes				(1,029,169)	(219,328)
Federal and state income taxes				(240,868)	(52,632)
Other comprehensive income, net of income taxes				(788,301)	(166,696)
Balance, End of Period		(718,526)	168,336	(718,526)	168,336
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 revenue, Investment securities				24,130
Operating expense, Personnel				0
Gain on available for sale securities, net				0	0
Other comprehensive income, before income taxes				(243,379)	0
Federal and state income taxes				(56,960)	0
Other comprehensive income, net of income taxes				(186,419)	0
Balance, End of Period		(186,419)	0	(186,419)	0
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 revenue, Investment securities				0
Operating expense, Personnel				(3,483)
Gain on available for sale securities, net				0	0
Other comprehensive income, before income taxes				(3,483)	0
Federal and state income taxes				(887)	0
Other comprehensive income, net of income taxes				(2,596)	0
Balance, End of Period		$ 0	$ 836	$ 0	$ 836
Subsequent Event [Member]
Dividends Payable, Date Declared	Nov. 01, 2022
Dividends declared (in dollars per share)	$ 0.54
Dividends Payable, Date to be Paid	Nov. 25, 2022
Dividends Payable, Date of Record	Nov. 15, 2022