STOCK-BASED COMPENSATION - Stock option activity (Details) - Stock options - $ / shares	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Number of Shares Underlying Options
Outstanding at beginning of period	201,720	213,078
Exercised	(10,160)	(11,358)
Outstanding at end of period	191,560	201,720
Weighted Average Exercise Price
Outstanding at beginning of period	$ 17.22	$ 16.92
Exercised	11.32	11.67
Outstanding at end of period	$ 17.53	$ 17.22

Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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