ACCUMULATED OTHER COMPREHENSIVE INCOME - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 677,471	$ 620,892	$ 657,184	$ 598,100
Net current period other comprehensive (loss) income	(11,339)	422	(16,812)	13,165
Ending balance	683,202	636,839	683,202	636,839
Accumulated Other Comprehensive Income (Loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	22,271	24,802	27,744	12,059
Other comprehensive income (loss) before reclassification	(11,385)	622	(16,318)	13,310
Amounts reclassified from accumulated other comprehensive income	46	(200)	(494)	(145)
Net current period other comprehensive (loss) income	(11,339)	422	(16,812)	13,165
Ending balance	10,932	25,224	10,932	25,224
Unrealized Gains and Losses on Available- for-Sales Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	23,619	26,256	29,182	13,607
Other comprehensive income (loss) before reclassification	(11,385)	622	(16,318)	13,310
Amounts reclassified from accumulated other comprehensive income	0	(248)	(630)	(287)
Net current period other comprehensive (loss) income	(11,385)	374	(16,948)	13,023
Ending balance	12,234	26,630	12,234	26,630
Defined Benefit Pension Items
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(1,348)	(1,454)	(1,438)	(1,548)
Other comprehensive income (loss) before reclassification	0	0	0	0
Amounts reclassified from accumulated other comprehensive income	46	48	136	142
Net current period other comprehensive (loss) income	46	48	136	142
Ending balance	$ (1,302)	$ (1,406)	$ (1,302)	$ (1,406)