Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total other comprehensive income (loss)	$ (37,199)	$ (221,380)	$ 71,676	$ (563,842)
Income tax benefit (expense)	7,811	46,490	(15,052)	118,407
Other comprehensive income (loss), net of tax	(29,388)	(174,890)	56,624	(445,435)
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Total reclassifications before tax	242,382	315,891	437,986	535,330
Income tax benefit (expense)	(51,328)	(66,623)	(92,385)	(111,049)
Total reclassifications, net of tax	191,054	249,268	345,601	424,281
Reclassification from Accumulated Other Comprehensive Income
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Total reclassifications before tax	(6,842)	(3,053)	(19,938)	1,290
Income tax benefit (expense)	1,437	641	4,187	(271)
Total reclassifications, net of tax	(5,405)	(2,412)	(15,751)	1,019
Accumulated other comprehensive income (loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other comprehensive income (loss), net of tax	(29,388)	(174,890)	56,624	(445,435)
Net unrealized gains and (losses) on available-for-sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total other comprehensive income (loss)	(38,270)	(222,000)	63,829	(564,960)
Income tax benefit (expense)	8,036	46,620	(13,404)	118,642
Other comprehensive income (loss), net of tax	(30,234)	(175,380)	50,425	(446,318)
Net unrealized gains and (losses) on available-for-sale securities | Reclassification from Accumulated Other Comprehensive Income
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Total reclassifications before tax	(5,771)	(2,433)	(9,935)	2,408
Income tax benefit (expense)	1,212	511	2,086	(506)
Total reclassifications, net of tax	(4,559)	(1,922)	(7,849)	1,902
Net benefit plan assets and (obligations) recognized in shareholders' equity
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total other comprehensive income (loss)	1,071	620	7,847	1,118
Income tax benefit (expense)	(225)	(130)	(1,648)	(235)
Other comprehensive income (loss), net of tax	846	490	6,199	883
Net benefit plan assets and (obligations) recognized in shareholders' equity | Reclassification from Accumulated Other Comprehensive Income
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Total reclassifications before tax	(1,071)	(620)	(10,003)	(1,118)
Income tax benefit (expense)	225	130	2,101	235
Total reclassifications, net of tax	$ (846)	$ (490)	$ (7,902)	$ (883)