COMPREHENSIVE INCOME - Components of AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (AOCI)
Beginning balance	$ 211,936	$ 176,773	$ 150,192
Other comprehensive income (loss) before reclassification	4,270	5,133
Amounts reclassified from AOCI	(723)	352
Total other comprehensive income (loss)	3,547	5,485	(3,074)
Ending balance	239,483	211,936	176,773
Unrealized gains (losses) on available for-sale securities
Accumulated Other Comprehensive Income (AOCI)
Beginning balance	2,942	(3,384)
Other comprehensive income (loss) before reclassification	5,344	6,204
Amounts reclassified from AOCI	(700)	122
Total other comprehensive income (loss)	4,644	6,326
Ending balance	7,586	2,942	(3,384)
Defined benefit pension plan items
Accumulated Other Comprehensive Income (AOCI)
Beginning balance	(4,295)	(3,422)
Other comprehensive income (loss) before reclassification	(1,074)	(1,071)
Amounts reclassified from AOCI	322	198
Total other comprehensive income (loss)	(752)	(873)
Ending balance	(5,047)	(4,295)	(3,422)
Investment hedge
Accumulated Other Comprehensive Income (AOCI)
Beginning balance	32	0
Other comprehensive income (loss) before reclassification	0	0
Amounts reclassified from AOCI	(345)	32
Total other comprehensive income (loss)	(345)	32
Ending balance	(313)	32	0
AOCI attributable to parent
Accumulated Other Comprehensive Income (AOCI)
Beginning balance	(1,321)	(6,806)	(2,988)
Total other comprehensive income (loss)	3,547	5,485	(3,074)
Ending balance	$ 2,226	$ (1,321)	$ (6,806)