ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Before and After Tax Amounts by Component (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Change in unrealized gain (loss) on securities:
Change in net unrealized gain during the period	$ 7,960	$ 3,344
Accretion of net unrealized loss on securities transferred to held-to-maturity	724	718
Credit loss expense	893
Net change	9,577	4,062
Tax expense	2,939	1,212
Net change in unrealized gain on securities, net of reclassification adjustments and tax	6,638	2,850
Change in pension and other postretirement obligations:
Reclassification adjustment for expense included in other expense	(87)	(317)
Change in the net actuarial gain	4,854	520
Net change	4,767	203
Tax expense	1,463	58
Net change in pension and other postretirement obligations	3,304	145
Change in unrealized gain (loss) on derivatives:
Change in net unrealized (loss) gain during the period	(7,567)	2,145
Reclassification adjustment for expense included in interest expense	1,840	2,435
Net change	(5,727)	4,580
Tax (benefit) expense	(1,758)	1,462
Net change in unrealized gain (loss) on derivatives, net of reclassification adjustments and tax	(3,969)	3,118
Total other comprehensive income, net of tax	$ 5,973	$ 6,113