ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net securities gains									$ 797	$ 433	$ 142
Other expense									8,905	8,197	9,806
Income tax expense	$ 5,507	$ 5,469	$ 5,705	$ 5,030	$ 6,071	$ 5,377	$ 4,448	$ 3,643	21,711	19,539	20,338
NET INCOME	$ 24,283	$ 24,119	$ 24,348	$ 22,983	$ 24,592	$ 22,776	$ 19,670	$ 17,299	95,733	84,337	87,047
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
NET INCOME									448	154	(41)
Reclassification out of Accumulated Other Comprehensive Income | Unrealized Gains and (Losses) on Available-for-Sales Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net securities gains									797	433	142
Income tax expense									(167)	(91)	(30)
NET INCOME									630	342	112
Reclassification out of Accumulated Other Comprehensive Income | Defined Benefit Pension Items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other expense									(242)	(251)	(205)
Income tax expense									60	63	52
NET INCOME									$ (182)	$ (188)	$ (153)