INCOME TAXES - Schedule of Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Allowance for credit losses	$ 31,181	$ 28,312
Unrealized capital loss on tax credit investments	2,688	1,603
Net unrealized loss on securities available for sale, swaps, and pension in OCI	50,704	63,335
Employee benefit plans	12,102	11,659
Purchase accounting adjustments	4,587	4,342
Net operating loss carryforwards	202	503
Deferred loan fees	5,654	4,049
Lease liability	13,583	14,148
Premises and equipment	1,188	2,630
Nonaccrual interest	890	1,069
Intangible amortization	1,020	659
Other	2,337	1,778
Deferred tax assets, net before valuation allowances	126,136	134,087
Valuation allowance	(400)	(400)
Deferred tax assets, net of valuation allowances	125,736	133,687
Deferred tax liabilities:
Loan servicing rights	(1,133)	(1,212)
Unamortized tax credit reserve	(1,661)	(1,687)
Right-of-use asset	(12,874)	(12,457)
Deferred tax liabilities	(15,668)	(15,356)
Deferred tax assets, net	$ 110,068	$ 118,331