ACCUMULATED OTHER COMPREHENSIVE INCOME - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 651,668	$ 606,572	$ 657,184	$ 598,100
Net current period other comprehensive (loss) income	7,161	2,252	(5,473)	12,743
Ending balance	677,471	620,892	677,471	620,892
Accumulated Other Comprehensive Income (Loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	15,110	22,550	27,744	12,059
Other comprehensive income (loss) before reclassification	7,151	2,244	(4,933)	12,688
Amounts reclassified from accumulated other comprehensive income	10	8	(540)	55
Net current period other comprehensive (loss) income	7,161	2,252	(5,473)	12,743
Ending balance	22,271	24,802	22,271	24,802
Unrealized Gains and Losses on Available- for-Sales Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	16,503	24,051	29,182	13,607
Other comprehensive income (loss) before reclassification	7,151	2,244	(4,933)	12,688
Amounts reclassified from accumulated other comprehensive income	(35)	(39)	(630)	(39)
Net current period other comprehensive (loss) income	7,116	2,205	(5,563)	12,649
Ending balance	23,619	26,256	23,619	26,256
Defined Benefit Pension Items
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(1,393)	(1,501)	(1,438)	(1,548)
Other comprehensive income (loss) before reclassification	0	0	0	0
Amounts reclassified from accumulated other comprehensive income	45	47	90	94
Net current period other comprehensive (loss) income	45	47	90	94
Ending balance	$ (1,348)	$ (1,454)	$ (1,348)	$ (1,454)