Accumulated Other Comprehensive Loss - Changes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Pre-tax Amount
Other comprehensive income (loss), Pre-tax Amount	$ (539,801)	$ (102,336)
Income Tax Benefit (Expense)
Other comprehensive income (loss), Income Tax Benefit (Expense)	143,992	27,297
Net of tax
Balance	2,656,912	2,744,104
Other comprehensive loss	(395,809)	(75,039)
Balance	2,285,149	2,683,630
Accumulated Other Comprehensive Income (Loss)
Pre-tax Amount
Accumulated other comprehensive income (loss), beginning balance, Pre-tax Amount	(165,967)	43,098
Accumulated other comprehensive (loss) income, ending balance, Pre-tax Amount	(705,768)	(59,238)
Income Tax Benefit (Expense)
Accumulated other comprehensive income (loss), beginning balance, Income Tax Benefit (Expense)	44,274	(11,494)
Accumulated other comprehensive loss, ending balance, Income Tax Benefit (Expense)	188,266	15,803
Net of tax
Balance	(121,693)	31,604
Other comprehensive loss	(395,809)	(75,039)
Balance	(517,502)	(43,435)
Pensions and Other Benefits
Net of tax
Balance	(24,390)	(31,737)
Balance	(24,390)	(31,737)
Investment Securities
Pre-tax Amount
Unrealized net gains (losses) arising during the period, Pre-tax Amount	(538,085)	(102,336)
Other comprehensive income (loss), Pre-tax Amount	(538,085)	(102,336)
Income Tax Benefit (Expense)
Unrealized net losses (gains) arising during the period, Income Tax Benefit (Expense)	143,534	27,297
Other comprehensive income (loss), Income Tax Benefit (Expense)	143,534	27,297
Net of tax
Balance	(97,303)	63,341
Unrealized net (losses) gains arising during the period, Net of tax	(394,551)	(75,039)
Other comprehensive loss	(394,551)	(75,039)
Balance	(491,854)	$ (11,698)
Cash Flow Derivative Hedges
Pre-tax Amount
Unrealized net gains (losses) arising during the period, Pre-tax Amount	(1,716)
Other comprehensive income (loss), Pre-tax Amount	(1,716)
Income Tax Benefit (Expense)
Unrealized net losses (gains) arising during the period, Income Tax Benefit (Expense)	458
Other comprehensive income (loss), Income Tax Benefit (Expense)	458
Net of tax
Unrealized net (losses) gains arising during the period, Net of tax	(1,258)
Other comprehensive loss	(1,258)
Balance	$ (1,258)