ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Before and After Tax Amounts by Component (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Change in unrealized gain (loss) on securities:
Change in net unrealized gain (loss) during the period	$ 3,344	$ (2,302)
Reclassification adjustment for net losses included in net loss on sale of securities and other assets		1,447
Accretion of net unrealized loss on securities transferred to held-to-maturity	718	757
Net change	4,062	(98)
Tax expense (benefit)	1,212	2,664
Net change in unrealized gain (loss) on securities, net of reclassification adjustments and tax	2,850	(2,762)
Change in pension and other postretirement obligations:
Reclassification adjustment for expense included in other expense	(317)	(370)
Change in the net actuarial gain	520	221
Net change	203	(149)
Tax expense (benefit)	58	(44)
Net change in pension and other postretirement obligations	145	(105)
Change in unrealized gain (loss) on derivatives:
Change in net unrealized (loss) gain during the period	2,145	(2,111)
Reclassification adjustment for expense included in interest expense	2,435	(313)
Net change	4,580	(2,424)
Tax expense (benefit)	1,462	(1,032)
Net change in unrealized gain (loss) on derivatives, net of reclassification adjustments and tax	3,118	(1,392)
Total other comprehensive income (loss), net of tax	$ 6,113	$ (4,259)