ACCUMULATED OTHER COMPREHENSIVE INCOME - Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net securities gains	$ 753	$ 0
Other expense	2,244	2,312
Income tax expense	5,030	3,643
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	550	(47)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains and Losses on Available-for-Sales Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net securities gains	753
Income tax expense	(158)
Net income	595
Reclassification out of Accumulated Other Comprehensive Income [Member] | Defined Benefit Pension Items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other expense	(60)	(63)
Income tax expense	15	16
Net income	$ (45)	$ (47)