Accumulated Other Comprehensive Loss - Changes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Pre-tax Amount
Other comprehensive income , Pre-tax Amount	$ 8,770	$ 37,607
Income Tax Benefit (Expense)
Other comprehensive loss, Income Tax Benefit (Expense)	(2,340)	(10,032)
Net of tax
Balance	2,486,066	2,269,005
Other comprehensive income	6,430	27,575
Balance	2,513,761	2,329,012
Accumulated other comprehensive Income (loss)
Pre-tax Amount
Accumulated other comprehensive loss, beginning balance, Pre-tax Amount	(723,100)	(871,813)
Accumulated other comprehensive loss, ending balance, Pre-tax Amount	(714,330)	(834,206)
Income Tax Benefit (Expense)
Accumulated other comprehensive loss, beginning balance, Income Tax Benefit (Expense)	192,890	232,559
Accumulated other comprehensive loss, ending balance, Income Tax Benefit (Expense)	190,550	222,527
Net of tax
Balance	(530,210)	(639,254)
Other comprehensive income	6,430	27,575
Balance	(523,780)	(611,679)
Pensions and Other Benefits
Net of tax
Balance	(5,373)	(5,431)
Balance	(5,373)	(5,431)
Investment securities
Pre-tax Amount
Unrealized net gains (losses) arising during the period, Pre-tax Amount	(3,432)	25,038
Other comprehensive income , Pre-tax Amount	7,728	36,746
Income Tax Benefit (Expense)
Unrealized net gains (losses) arising during the period, Income Tax Benefit (Expense)	915	(6,679)
Other comprehensive loss, Income Tax Benefit (Expense)	(2,061)	(9,802)
Net of tax
Unrealized net gains (losses) arising during the period, Net of tax	(2,517)	18,359
Other comprehensive income	5,667	26,944
Amortization of unrealized holding losses on held-to-maturity securities
Pre-tax Amount
Reclassification of net losses (gains) to net income, Pre-tax Amount	11,160	11,708
Income Tax Benefit (Expense)
Reclassification of net (losses) gains to net income, Income Tax Benefit (Expense)	(2,976)	(3,123)
Net of tax
Reclassification of net gains (losses) to net income, Net of tax	8,184	8,585
Cash Flow Derivative Hedges.
Pre-tax Amount
Unrealized net gains (losses) arising during the period, Pre-tax Amount	(713)	(442)
Reclassification of net losses (gains) to net income, Pre-tax Amount	1,755	1,303
Other comprehensive income , Pre-tax Amount	1,042	861
Income Tax Benefit (Expense)
Unrealized net gains (losses) arising during the period, Income Tax Benefit (Expense)	189	118
Reclassification of net (losses) gains to net income, Income Tax Benefit (Expense)	(468)	(348)
Other comprehensive loss, Income Tax Benefit (Expense)	(279)	(230)
Net of tax
Balance	(803)	(4,702)
Unrealized net gains (losses) arising during the period, Net of tax	(524)	(324)
Reclassification of net gains (losses) to net income, Net of tax	1,287	955
Other comprehensive income	763	631
Balance	(40)	(4,071)
Available-for-sale Investment securities
Net of tax
Balance	(222,423)	(292,175)
Other comprehensive income	(2,517)	18,359
Balance	$ (224,940)	$ (273,816)