Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 547,459	$ 491,723	$ 457,371
OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax [Abstract]
Unrealized (losses) gains on securities available for sale arising during the period	(80,951)	155,009	64,644
Tax effect	18,619	(35,652)	(14,868)
Reclassification adjustment for realized gains on securities available for sale included in income before income taxes	(33,119)	(60,253)	(7,115)
Tax effect	7,617	13,858	1,636
Unrealized (losses) gains on securities available for sale arising during the period, net of tax	(87,834)	72,962	44,297
Unrealized losses on securities available for sale transferred to held to maturity [Abstract]
Unrealized (losses) gains on securities available for sale transferred to held to maturity	(12,659)	5,894	72,512
Tax effect	2,912	(1,356)	(16,678)
Reclassification adjustment for (amortization) accretion of unrealized (losses) gains on securities available for sale transferred to held to maturity	(1,475)	(495)	19,889
Tax effect	339	114	(4,574)
Total change in unrealized (losses) gains on securities available for sale transferred to held to maturity, net of tax	(10,883)	4,157	71,149
Defined benefit pension items:
Actuarial gains (loss) arising during the period	97,880	55,023	(20,049)
Tax effect	(22,512)	(12,656)	4,611
Amortization of actuarial gains (losses) and prior service cost	27,093	25,324	10,981
Other Comprehensive Income (Loss), Defined Benefit Plan, Amortization of Gains (Losses) And Prior Service Cost, Tax	6,231	5,824	2,525
Total change from defined benefit plans, net of tax	(96,230)	(61,867)	6,982
Net current period other comprehensive (loss) income	(2,487)	138,986	108,464
Total comprehensive income	$ 544,972	$ 630,709	$ 565,835