Accumulated Other Comprehensive Income (Loss) - Changes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Pre-tax Amount
Other comprehensive income (loss), Pre-tax Amount	$ (705,846)	$ (209,065)	$ 86,548
Income Tax Benefit (Expense)
Other comprehensive income (loss), Income Tax Benefit (Expense)	188,285	55,768	(23,195)
Net of tax
Balance	2,656,912	2,744,104	2,640,258
Other comprehensive (loss) income	(517,561)	(153,297)	63,353
Balance	2,269,005	2,656,912	2,744,104
Accumulated Other Comprehensive Income (Loss)
Pre-tax Amount
Accumulated other comprehensive income (loss), beginning balance, Pre-tax Amount	(165,967)	43,098	(43,450)
Accumulated other comprehensive (loss) income, ending balance, Pre-tax Amount	(871,813)	(165,967)	43,098
Income Tax Benefit (Expense)
Accumulated other comprehensive income (loss), beginning balance, Income Tax Benefit (Expense)	44,274	(11,494)	11,701
Accumulated other comprehensive loss, ending balance, Income Tax Benefit (Expense)	232,559	44,274	(11,494)
Net of tax
Balance	(121,693)	31,604	(31,749)
Other comprehensive (loss) income	(517,561)	(153,297)	63,353
Balance	(639,254)	(121,693)	31,604
Pensions and Other Benefits
Pre-tax Amount
Unrealized net gains (losses) arising during the period, Pre-tax Amount	25,856	10,020	(4,855)
Income Tax Benefit (Expense)
Unrealized net losses (gains) arising during the period, Income Tax Benefit (Expense)	(6,897)	(2,673)	1,200
Net of tax
Balance	(24,390)	(31,737)	(28,082)
Unrealized net (losses) gains arising during the period, Net of tax	18,959	7,347	(3,655)
Other comprehensive (loss) income	18,959	7,347	(3,655)
Balance	(5,431)	(24,390)	(31,737)
Pension and other benefits, net actuarial losses arising during the year
Pre-tax Amount
Unrealized net gains (losses) arising during the period, Pre-tax Amount	20,710	3,107	(10,399)
Income Tax Benefit (Expense)
Unrealized net losses (gains) arising during the period, Income Tax Benefit (Expense)	(5,524)	(829)	2,774
Net of tax
Unrealized net (losses) gains arising during the period, Net of tax	15,186	2,278	(7,625)
Pension and other benefits, prior service credit
Pre-tax Amount
Unrealized net gains (losses) arising during the period, Pre-tax Amount			(51)
Income Tax Benefit (Expense)
Unrealized net losses (gains) arising during the period, Income Tax Benefit (Expense)			14
Net of tax
Unrealized net (losses) gains arising during the period, Net of tax			(37)
Pension and other benefits: Amortization of net loss included in net income
Pre-tax Amount
Unrealized net gains (losses) arising during the period, Pre-tax Amount	5,146	6,913	5,595
Income Tax Benefit (Expense)
Unrealized net losses (gains) arising during the period, Income Tax Benefit (Expense)	(1,373)	(1,844)	(1,492)
Net of tax
Unrealized net (losses) gains arising during the period, Net of tax	3,773	5,069	4,103
Pension and other benefits, change in Company tax rate
Income Tax Benefit (Expense)
Unrealized net losses (gains) arising during the period, Income Tax Benefit (Expense)			(96)
Net of tax
Unrealized net (losses) gains arising during the period, Net of tax			(96)
Investment Securities
Pre-tax Amount
Unrealized net gains (losses) arising during the period, Pre-tax Amount			91,403
Reclassification of net losses (gains) to net income, Pre-tax Amount		(102)	114
Other comprehensive income (loss), Pre-tax Amount		(219,085)
Income Tax Benefit (Expense)
Unrealized net losses (gains) arising during the period, Income Tax Benefit (Expense)			(24,395)
Reclassification of net gains (losses) to net income, Income Tax Benefit (Expense)		(27)	30
Other comprehensive income (loss), Income Tax Benefit (Expense)	193,471	58,441
Net of tax
Balance	(97,303)	63,341	(3,667)
Unrealized net (losses) gains arising during the period, Net of tax			67,008
Reclassification of net (gains) losses to net income, Net of tax		(75)	84
Other comprehensive (loss) income	(567,291)	(160,644)	67,008
Balance	(292,175)	(97,303)	63,341
Investment securities: Unrealized net losses arising during the year
Pre-tax Amount
Unrealized net gains (losses) arising during the period, Pre-tax Amount	(773,667)	(218,983)	91,289
Income Tax Benefit (Expense)
Unrealized net losses (gains) arising during the period, Income Tax Benefit (Expense)	206,376	58,414	(24,365)
Net of tax
Unrealized net (losses) gains arising during the period, Net of tax	(567,291)	$ (160,569)	$ 66,924
Investment securities: Amortization of unrealized holding losses on held-to-maturity securities
Pre-tax Amount
Reclassification of net losses (gains) to net income, Pre-tax Amount	48,378
Income Tax Benefit (Expense)
Reclassification of net gains (losses) to net income, Income Tax Benefit (Expense)	(12,905)
Net of tax
Reclassification of net (gains) losses to net income, Net of tax	35,473
Investment Securities (including reclassification of net losses to net income)
Pre-tax Amount
Other comprehensive income (loss), Pre-tax Amount	(725,289)
Net of tax
Other comprehensive (loss) income	(531,818)
Cash Flow Derivative Hedges
Pre-tax Amount
Unrealized net gains (losses) arising during the period, Pre-tax Amount	(6,710)
Reclassification of net losses (gains) to net income, Pre-tax Amount	297
Other comprehensive income (loss), Pre-tax Amount	(6,413)
Income Tax Benefit (Expense)
Unrealized net losses (gains) arising during the period, Income Tax Benefit (Expense)	1,790
Reclassification of net gains (losses) to net income, Income Tax Benefit (Expense)	(79)
Other comprehensive income (loss), Income Tax Benefit (Expense)	1,711
Net of tax
Unrealized net (losses) gains arising during the period, Net of tax	(4,920)
Reclassification of net (gains) losses to net income, Net of tax	218
Other comprehensive (loss) income	(4,702)
Balance	$ (4,702)