ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Schedule of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other comprehensive income, before tax	$ 9,814	$ 15,721
Income tax expense	(2,682)	(4,331)
Total other comprehensive income, net of taxes	7,132	11,390
Accumulated Other Comprehensive Loss, net of income taxes
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other comprehensive income, before tax	9,814	15,721
Income tax expense	(2,682)	(4,331)
Total other comprehensive income, net of taxes	7,132	11,390
Unrealized gains (losses) on benefits plans
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other comprehensive income, before tax	43	48
Income tax expense	(11)	(13)
Total other comprehensive income, net of taxes	32	35
Unrealized gains (losses) on available for sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other comprehensive income, before tax	9,771	15,673
Income tax expense	(2,671)	(4,318)
Total other comprehensive income, net of taxes	7,100	11,355
Unrealized holding gains on available for sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other comprehensive income (loss), before reclassifications, before tax	6,402	12,099
Reclassification adjustment for losses realized in loss on sale of securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification adjustment	2,774	3,086
Accretion of net unrealized loss on securities transferred to held-to-maturity recognized in interest income from securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification adjustment	595	488
Other comprehensive income, before tax	595	488
Income tax expense	(163)	(134)
Postemployment Retirement Benefits | Change in obligation for postretirement benefits and for prior service credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other comprehensive income (loss), before reclassifications, before tax	36	40
Postemployment Retirement Benefits | Reclassification adjustment for prior service expense included in compensation and employee benefits
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification adjustment	7	7
Other Postretirement Benefits Plan | Unrealized gains (losses) on benefits plans
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other comprehensive income, before tax	$ 0	$ 1