Other Comprehensive Income (Loss) - Pretax and Related Income Tax Benefit (Expense) Components (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Total reclassifications	$ 902,229	$ 1,090,034	$ 801,777
Income tax benefit (expense)	(189,280)	(224,685)	(166,794)
Net income	712,949	865,349	634,983
Reclassification from Accumulated Other Comprehensive Income
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Total reclassifications	(41,090)	(26,610)	676
Income tax benefit (expense)	8,629	5,588	(142)
Net income	(32,461)	(21,022)	534
Reclassification from Accumulated Other Comprehensive Income | Net unrealized gains and losses on available-for-sale securities
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Total reclassifications	(27,100)	(9,860)	10,455
Income tax benefit (expense)	5,691	2,070	(2,195)
Net income	(21,409)	(7,790)	8,260
Reclassification from Accumulated Other Comprehensive Income | Net benefit plan assets and obligations recognized in shareholders' equity
Amounts Reclassified From Accumulated Other Comprehensive Income [Abstract]
Total reclassifications	(13,990)	(16,750)	(9,779)
Income tax benefit (expense)	2,938	3,518	2,053
Net income	$ (11,052)	$ (13,232)	$ (7,726)