Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total other comprehensive income (loss)	$ 108,875	$ (342,462)
Income tax benefit (expense)	(22,863)	71,917
Other comprehensive income (loss), net of tax	86,012	(270,545)
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Total reclassifications before tax	195,604	219,439
Income tax benefit (expense)	(41,057)	(44,426)
Total reclassifications, net of tax	154,547	175,013
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	4,642,740
Other comprehensive income (loss) before reclassifications	75,666
Less: Amounts reclassified from AOCI	(10,346)
Balance, end of period	4,777,644	4,610,355
Reclassification from Accumulated Other Comprehensive Income
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Total reclassifications before tax	(13,096)	4,343
Income tax benefit (expense)	2,750	(912)
Total reclassifications, net of tax	(10,346)	3,431
Accumulated other comprehensive income (loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other comprehensive income (loss), net of tax	86,012	(270,545)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(481,511)	119,697
Balance, end of period	(395,499)	(150,848)
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)	102,099	(342,960)
Income tax benefit (expense)	(21,440)	72,022
Other comprehensive income (loss), net of tax	80,659	(270,938)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(408,496)
Other comprehensive income (loss) before reclassifications	77,369
Less: Amounts reclassified from AOCI	(3,290)
Balance, end of period	(327,837)
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	(4,164)	4,841
Income tax benefit (expense)	874	(1,017)
Total reclassifications, net of tax	(3,290)	3,824
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)	6,776	498
Income tax benefit (expense)	(1,423)	(105)
Other comprehensive income (loss), net of tax	5,353	393
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(73,015)
Other comprehensive income (loss) before reclassifications	(1,703)
Less: Amounts reclassified from AOCI	(7,056)
Balance, end of period	(67,662)
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	(8,932)	(498)
Income tax benefit (expense)	1,876	105
Total reclassifications, net of tax	$ (7,056)	$ (393)