Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current [Abstract]
Federal	$ 35,483	$ 36,358	$ 28,475
State	8,626	9,768	7,653
Total Current	44,109	46,126	36,128
Deferred [Abstract]
Federal	507	(14,021)	(1,379)
State	357	(3,406)	(338)
Total Deferred	864	(17,427)	(1,717)
Total income tax expense	44,973	28,699	34,411
Deferred tax assets [Abstract]
Allowance for loan losses	22,479	27,282
Lease liability	6,744	8,141
Deferred compensation	9,584	11,602
Postretirement benefit obligation	1,286	1,511
Fair value adjustments from acquisitions	199	259
Loan fees	12,936	5,400
Accrued liabilities	1,424	1,307
Stock-based compensation expense	2,679	3,213
Unrealized losses on securities	1,482	0
Other	4,200	3,558
Total deferred tax assets	63,013	62,273
Deferred tax liabilities [Abstract]
Pension benefits	16,137	14,406
Lease right-of-use asset	5,681	6,567
Amortization of intangible assets	13,187	12,725
Premises and equipment, primarily due to accelerated depreciation	4,962	4,774
Unrealized gain on securities	0	7,732
Other	1,008	952
Total deferred tax liabilities	40,975	47,156
Net deferred tax asset at year-end	22,038	15,117	2,534
Net deferred tax asset at beginning of year	15,117	2,534
Increase in net deferred tax asset	6,921	12,583
Income tax reconciliation [Abstract]
Federal income tax at statutory rate	41,971	27,948	32,641
Tax exempt income	(1,014)	(981)	(1,233)
Net increase in cash surrender value of life insurance	(1,230)	(1,135)	(927)
Federal tax credits	(1,884)	(1,705)	(1,458)
State taxes, net of federal tax benefit	7,097	5,026	5,773
Stock-based compensation, excess tax benefit	(323)	(152)	(342)
Other, net	356	(302)	(43)
Total income tax expense	44,973	28,699	34,411
Reconciliation of gross unrecognized tax benefits [Roll Forward]
Beginning balance	1,178	779
Additions for tax positions of prior years	80	254
Current period tax positions	287	145
Ending balance	1,545	1,178	$ 779
Amount that would affect the effective tax rate if recognized, gross of tax	$ 1,221	$ 931
State and Local Jurisdiction [Member]
Income Tax Examination [Abstract]
Tax years under examination	2015 2016 2017 2018 2019