Accumulated Other Comprehensive Income (Loss) - Changes, Net of Tax (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Net of tax
Balance	$ 2,656,912,000	$ 2,744,104,000	$ 2,640,258,000
Unrealized net losses related to the transfer of securities from available-for-sale to held-to-maturity	(372,400,000)
Other comprehensive (loss) income	(517,561,000)	(153,297,000)	63,353,000
Balance	2,269,005,000	2,656,912,000	2,744,104,000
Incremental non-credit-related impairment loss recognized in earnings on securities	0	0	0
Accumulated Other Comprehensive Income (Loss)
Net of tax
Balance	(121,693,000)	31,604,000	(31,749,000)
Other comprehensive (loss) income	(517,561,000)	(153,297,000)	63,353,000
Balance	(639,254,000)	(121,693,000)	31,604,000
Pensions and Other Benefits
Net of tax
Balance	(24,390,000)	(31,737,000)	(28,082,000)
Other comprehensive (loss) income	18,959,000	7,347,000	(3,655,000)
Balance	(5,431,000)	(24,390,000)	(31,737,000)
Available-for-sale Investment securities
Net of tax
Balance	(97,303,000)	63,341,000	(3,667,000)
Unrealized net losses related to the transfer of securities from available-for-sale to held-to-maturity	372,419,000
Other comprehensive (loss) income	(567,291,000)	(160,644,000)	67,008,000
Balance	(292,175,000)	$ (97,303,000)	$ 63,341,000
Held-to-Maturity Investment Securities
Net of tax
Unrealized net losses related to the transfer of securities from available-for-sale to held-to-maturity	(372,419,000)
Other comprehensive (loss) income	35,473,000
Balance	(336,946,000)
Cash Flow Derivative Hedges
Net of tax
Other comprehensive (loss) income	(4,702,000)
Balance	$ (4,702,000)