Income Taxes - Summary of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Allowance for credit losses	$ 128,717	$ 133,459
Employee benefits	41,190	39,917
Investment securities	42,361	48,598
Net operating loss carryforwards	11,037	13,904
Purchase accounting	53,980	66,487
FDIC Special Assessment	13,894	0
Other	24,362	12,995
Total deferred tax assets	315,541	315,360
Deferred tax liabilities:
Pension plans	37,194	30,474
Depreciation	20,963	16,625
Other investments	11,175	8,838
Core deposit intangibles	28,237	36,189
Other	22,319	27,235
Total deferred tax liabilities	119,888	119,361
Valuation Allowance	424	1,642
Net deferred tax asset (included in other assets)	$ 195,229	$ 194,357