Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total other comprehensive income (loss)	$ (214,920)	$ (27,389)	$ (778,762)	$ (87,565)
Income tax benefit (expense)	45,133	5,752	163,540	18,389
Other comprehensive income (loss), net of tax	(169,787)	(21,637)	(615,222)	(69,176)
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Total reclassifications before tax	314,267	199,732	849,597	583,217
Income tax benefit (expense)	(64,642)	(41,755)	(175,691)	(122,168)
Total reclassifications, net of tax	249,625	157,977	673,906	461,049
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period			4,861,382
Other comprehensive income (loss) before reclassifications			(624,401)
Less: Amounts reclassified from AOCI			(9,179)
Balance, end of period	4,540,061	4,877,420	4,540,061	4,877,420
Reclassification from Accumulated Other Comprehensive Income
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Total reclassifications before tax	(12,909)	74	(11,619)	4,547
Income tax benefit (expense)	2,711	(15)	2,440	(954)
Total reclassifications, net of tax	(10,198)	59	(9,179)	3,593
Accumulated other comprehensive income (loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other comprehensive income (loss), net of tax	(169,787)	(21,637)	(615,222)	(69,176)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(325,738)	169,282	119,697	216,821
Balance, end of period	(495,525)	147,645	(495,525)	147,645
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)	(194,449)	(34,937)	(759,409)	(97,057)
Income tax benefit (expense)	40,834	7,337	159,476	20,382
Other comprehensive income (loss), net of tax	(153,615)	(27,600)	(599,933)	(76,675)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period			150,038
Other comprehensive income (loss) before reclassifications			(603,309)
Less: Amounts reclassified from AOCI			(3,376)
Balance, end of period	(449,895)		(449,895)
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	(6,681)	1,045	(4,273)	7,462
Income tax benefit (expense)	1,403	(219)	897	(1,566)
Total reclassifications, net of tax	(5,278)	826	(3,376)	5,896
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)	(20,471)	7,548	(19,353)	9,492
Income tax benefit (expense)	4,299	(1,585)	4,064	(1,993)
Other comprehensive income (loss), net of tax	(16,172)	5,963	(15,289)	7,499
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period			(30,341)
Other comprehensive income (loss) before reclassifications			(21,092)
Less: Amounts reclassified from AOCI			(5,803)
Balance, end of period	(45,630)		(45,630)
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	(6,228)	(971)	(7,346)	(2,915)
Income tax benefit (expense)	1,308	204	1,543	612
Total reclassifications, net of tax	$ (4,920)	$ (767)	$ (5,803)	$ (2,303)