Income Taxes - Summary of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Allowance for credit losses	$ 102,704	$ 96,508
Employee benefits	22,587	20,888
Net operating loss carryforwards	15,859	17,814
Purchase accounting	8,971	10,354
Other	11,689	24,677
Total deferred tax assets	161,810	170,241
Deferred tax liabilities:
Pension plans	30,119	22,705
Depreciation	10,343	3,829
Investment securities	3,728	12,690
Other investments	12,069	9,584
Core deposit intangibles	11,888	12,960
Other	14,133	12,226
Total deferred tax liabilities	82,280	73,994
Valuation Allowance	916	916
Net deferred tax asset (included in other assets)	$ 78,614	$ 95,331