Accumulated Other Comprehensive Loss - Changes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Pre-tax Amount
Other comprehensive income (loss), Pre-tax Amount	$ (1,441)	$ (73,584)	$ 36,166	$ (613,385)
Income Tax Benefit (Expense)
Other comprehensive income (loss), Income Tax Benefit (Expense)	384	19,629	(9,648)	163,621
Net of tax
Balance	2,329,012	2,285,149	2,269,005	2,656,912
Other comprehensive (loss) income	(1,057)	(53,955)	26,518	(449,764)
Balance	2,359,738	2,252,611	2,359,738	2,252,611
Accumulated Other Comprehensive Income (Loss)
Pre-tax Amount
Accumulated other comprehensive income (loss), beginning balance, Pre-tax Amount	(834,206)	(705,768)	(871,813)	(165,967)
Accumulated other comprehensive (loss) income, ending balance, Pre-tax Amount	(835,647)	(779,352)	(835,647)	(779,352)
Income Tax Benefit (Expense)
Accumulated other comprehensive income (loss), beginning balance, Income Tax Benefit (Expense)	222,527	188,266	232,559	44,274
Accumulated other comprehensive loss, ending balance, Income Tax Benefit (Expense)	222,911	207,895	222,911	207,895
Net of tax
Balance	(611,679)	(517,502)	(639,254)	(121,693)
Other comprehensive (loss) income	(1,057)	(53,955)	26,518	(449,764)
Balance	(612,736)	(571,457)	(612,736)	(571,457)
Pensions and Other Benefits
Net of tax
Balance	(5,431)	(24,390)	(5,431)	(24,390)
Balance	(5,431)	(24,390)	(5,431)	(24,390)
Investment securities
Pre-tax Amount
Unrealized net gains (losses) arising during the period, Pre-tax Amount	(14,025)	(91,352)	11,013	(629,437)
Reclassification of net losses (gains) to net income, Pre-tax Amount	13,064	19,929	24,772	19,929
Other comprehensive income (loss), Pre-tax Amount	(961)	(71,423)	35,785	(609,508)
Income Tax Benefit (Expense)
Unrealized net losses (gains) arising during the period, Income Tax Benefit (Expense)	3,741	24,369	(2,938)	167,903
Reclassification of net (losses) gains to net income, Income Tax Benefit (Expense)	(3,485)	(5,317)	(6,608)	(5,317)
Other comprehensive income (loss), Income Tax Benefit (Expense)	256	19,052	(9,546)	162,586
Net of tax
Unrealized net (losses) gains arising during the period, Net of tax	(10,284)	(66,983)	8,075	(461,534)
Reclassification of net (gains) losses to net income, Net of tax	9,579	14,612	18,164	14,612
Other comprehensive (loss) income	(705)	(52,371)	26,239	(446,922)
Cash Flow Derivative Hedges
Pre-tax Amount
Unrealized net gains (losses) arising during the period, Pre-tax Amount	(2,053)	(1,523)	(2,495)	(3,239)
Reclassification of net losses (gains) to net income, Pre-tax Amount	1,573	(638)	2,876	(638)
Other comprehensive income (loss), Pre-tax Amount	(480)	(2,161)	381	(3,877)
Income Tax Benefit (Expense)
Unrealized net losses (gains) arising during the period, Income Tax Benefit (Expense)	548	407	665	865
Reclassification of net (losses) gains to net income, Income Tax Benefit (Expense)	(420)	170	(767)	170
Other comprehensive income (loss), Income Tax Benefit (Expense)	128	577	(102)	1,035
Net of tax
Balance	(4,071)	(1,258)	(4,702)
Unrealized net (losses) gains arising during the period, Net of tax	(1,505)	(1,116)	(1,830)	(2,374)
Reclassification of net (gains) losses to net income, Net of tax	1,153	(468)	2,109	(468)
Other comprehensive (loss) income	(352)	(1,584)	279	(2,842)
Balance	$ (4,423)	$ (2,842)	$ (4,423)	$ (2,842)