Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Allowance for credit losses	$ 15,507	$ 14,990
Post-retirement benefits	6,602	6,002
Deferred compensation	2,122	3,619
Retirement Income Maintenance plan	3,222	3,062
ESOP	1,131	990
Stock-based compensation	2,968	2,386
Reserve for uncollected interest	213	35
Net unrealized losses on debt securities and defined benefit plans	62,070	70,060
Federal and State NOLs	14,607	13,333
Alternative minimum assessment carryforwards	2,156	2,156
Charitable contribution carryforward	0	3,514
Purchase accounting	1,428	2,805
Lease liability	4,654	5,264
Other items	4,744	7,002
Gross deferred tax assets	121,424	135,218
Valuation allowance	(26)	(1,965)
Total deferred tax assets, net	121,398	133,253
Deferred tax liabilities:
Pension expense	72,307	68,825
Depreciation	2,996	5,945
Deferred loan costs	14,006	14,724
Intangible assets	1,609	1,616
Lease right-of-use asset	4,371	4,958
Other items	618	286
Total gross deferred tax liabilities	95,907	96,354
Net deferred tax asset (liability)	$ 25,491	$ 36,899