ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	$ 620,892	$ 565,363	$ 598,100	$ 521,704
Net current period other comprehensive income	422	3,967	13,165	19,658
Balance	636,839	584,436	636,839	584,436
Accumulated Other Comprehensive Income (Loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	24,802	9,500	12,059	(6,191)
Other comprehensive income before reclassification	688	3,934	13,386	19,636
Amounts reclassified from accumulated other comprehensive income	(266)	33	(221)	22
Net current period other comprehensive income	422	3,967	13,165	19,658
Balance	25,224	13,467	25,224	13,467
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	26,256	10,818	13,607	(4,796)
Other comprehensive income before reclassification	688	3,934	13,386	19,636
Amounts reclassified from accumulated other comprehensive income	(314)	(6)	(363)	(94)
Net current period other comprehensive income	374	3,928	13,023	19,542
Balance	26,630	14,746	26,630	14,746
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	(1,454)	(1,318)	(1,548)	(1,395)
Other comprehensive income before reclassification	0	0	0	0
Amounts reclassified from accumulated other comprehensive income	48	39	142	116
Net current period other comprehensive income	48	39	142	116
Balance	$ (1,406)	$ (1,279)	$ (1,406)	$ (1,279)