Accumulated Other Comprehensive Loss - Changes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Pre-tax Amount
Reclassification of net losses (gains) to net income, Pre-tax Amount				$ (102)
Other comprehensive income (loss), Pre-tax Amount	$ (73,584)	$ 18,729	$ (613,385)	(83,607)
Income Tax Benefit (Expense)
Reclassification of net gains (losses) to net income, Income Tax Benefit (Expense)				27
Other comprehensive income (loss), Income Tax Benefit (Expense)	19,629	(4,996)	163,621	22,301
Net of tax
Balance	2,285,149	2,683,630	2,656,912	2,744,104
Reclassification of net (gains) losses to net income, Net of tax				(75)
Other comprehensive (loss) income	(53,955)	13,733	(449,764)	(61,306)
Balance	2,252,611	2,731,341	2,252,611	2,731,341
Accumulated Other Comprehensive Income (Loss)
Pre-tax Amount
Accumulated other comprehensive income (loss), beginning balance, Pre-tax Amount	(705,768)	(59,238)	(165,967)	43,098
Accumulated other comprehensive (loss) income, ending balance, Pre-tax Amount	(779,352)	(40,509)	(779,352)	(40,509)
Income Tax Benefit (Expense)
Accumulated other comprehensive income (loss), beginning balance, Income Tax Benefit (Expense)	188,266	15,803	44,274	(11,494)
Accumulated other comprehensive loss, ending balance, Income Tax Benefit (Expense)	207,895	10,807	207,895	10,807
Net of tax
Balance	(517,502)	(43,435)	(121,693)	31,604
Other comprehensive (loss) income	(53,955)	13,733	(449,764)	(61,306)
Balance	(571,457)	(29,702)	(571,457)	(29,702)
Pensions and Other Benefits
Net of tax
Balance	(24,390)	(31,737)	(24,390)	(31,737)
Balance	(24,390)	(31,737)	(24,390)	(31,737)
Investment Securities
Pre-tax Amount
Unrealized net gains (losses) arising during the period, Pre-tax Amount	(91,352)	18,831	(629,437)	(83,505)
Reclassification of net losses (gains) to net income, Pre-tax Amount	19,929	(102)	19,929
Other comprehensive income (loss), Pre-tax Amount	(71,423)	18,729	(609,508)	(83,607)
Income Tax Benefit (Expense)
Unrealized net losses (gains) arising during the period, Income Tax Benefit (Expense)	24,369	(5,023)	167,903	22,274
Reclassification of net gains (losses) to net income, Income Tax Benefit (Expense)	(5,317)	27	(5,317)
Other comprehensive income (loss), Income Tax Benefit (Expense)	19,052	(4,996)	162,586	22,301
Net of tax
Unrealized net (losses) gains arising during the period, Net of tax	(66,983)	13,808	(461,534)	(61,231)
Reclassification of net (gains) losses to net income, Net of tax	14,612	(75)	14,612
Other comprehensive (loss) income	(52,371)	13,733	(446,922)	(61,306)
Available-for-sale Investment securities
Net of tax
Balance	(491,854)	(11,698)	(97,303)	63,341
Other comprehensive (loss) income	(66,983)	13,733	(461,534)	(61,306)
Balance	(220,021)	$ 2,035	(220,021)	$ 2,035
Cash Flow Derivative Hedges
Pre-tax Amount
Unrealized net gains (losses) arising during the period, Pre-tax Amount	(1,523)		(3,239)
Reclassification of net losses (gains) to net income, Pre-tax Amount	(638)		(638)
Other comprehensive income (loss), Pre-tax Amount	(2,161)		(3,877)
Income Tax Benefit (Expense)
Unrealized net losses (gains) arising during the period, Income Tax Benefit (Expense)	407		865
Reclassification of net gains (losses) to net income, Income Tax Benefit (Expense)	(170)		(170)
Other comprehensive income (loss), Income Tax Benefit (Expense)	577		1,035
Net of tax
Balance	(1,258)
Unrealized net (losses) gains arising during the period, Net of tax	(1,116)		(2,374)
Reclassification of net (gains) losses to net income, Net of tax	(468)		(468)
Other comprehensive (loss) income	(1,584)		(2,842)
Balance	$ (2,842)		$ (2,842)