STOCK BASED COMPENSATION PLANS - Stock Units Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Weighted Average Grant Date Fair Value
Unrecognized compensation cost	$ 0
Performance stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance period required	3 years	3 years
Number of Units Outstanding
Beginning balance (in shares)	43,058	37,865
Awarded (in shares)	25,041	17,968
Vested (in shares)	(10,369)	(11,801)
Forfeited (in shares)	(1,402)	(974)
Ending balance (in shares)	56,328	43,058	37,865
Weighted Average Grant Date Fair Value
Beginning balance (usd per share)	$ 26.01	$ 26.77
Granted (usd per share)	25.07	23.24
Vested (usd per share)	18.51	23.92
Forfeited (usd per share)	29.13	28.78
Ending balance (usd per share)	$ 24.98	$ 26.01	$ 26.77
Intrinsic value of stock units vested and exercised	$ 174	$ 376	$ 337
Performance stock units \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant under this plan	0	0
Performance stock units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant under this plan	37,562	26,956
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Number of Units Outstanding
Beginning balance (in shares)	106,552	80,740
Awarded (in shares)	63,667	50,352
Vested (in shares)	(31,565)	(19,411)
Forfeited (in shares)	(7,256)	(5,129)
Ending balance (in shares)	131,398	106,552	80,740
Weighted Average Grant Date Fair Value
Beginning balance (usd per share)	$ 25.82	$ 28.24
Granted (usd per share)	21.98	22.45
Vested (usd per share)	27.38	26.11
Forfeited (usd per share)	25.60	29.28
Ending balance (usd per share)	$ 23.57	$ 25.82	$ 28.24
Intrinsic value of stock units vested and exercised	$ 600	$ 493	$ 594
Unrecognized compensation cost	$ 2,200
Unrecognized compensation cost, expense recognition period	1 year 7 months 13 days
Restricted stock units \| Minimum
Weighted Average Grant Date Fair Value
Granted (usd per share)	$ 20.44	$ 22.07
Restricted stock units \| Maximum
Weighted Average Grant Date Fair Value
Granted (usd per share)	$ 25.07	$ 24.67

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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