Income Taxes - Summary of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Allowance for credit losses	$ 133,459	$ 102,704
Employee benefits	39,917	22,587
Investment securities	48,598	0
Net operating loss carryforwards	13,904	15,859
Purchase accounting	66,487	8,971
Other	12,995	11,689
Total deferred tax assets	315,360	161,810
Deferred tax liabilities:
Pension plans	30,474	30,119
Depreciation	16,625	10,343
Investment securities	0	3,728
Other investments	8,838	12,069
Core deposit intangibles	36,189	11,888
Other	27,235	14,133
Total deferred tax liabilities	119,361	82,280
Valuation Allowance	1,642	916
Net deferred tax asset (included in other assets)	$ 194,357	$ 78,614