EARNINGS PER SHARE - Earnings Per Share Computations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Net income	$ 24,283	$ 24,119	$ 24,348	$ 22,983	$ 24,592	$ 22,776	$ 19,670	$ 17,299	$ 95,733	$ 84,337	$ 87,047
Weighted-average common shares outstanding (in shares)									25,475,994	25,469,242	25,588,404
Basic earnings per common share (in USD per share)	$ 0.95	$ 0.95	$ 0.96	$ 0.90	$ 0.97	$ 0.89	$ 0.77	$ 0.68	$ 3.76	$ 3.31	$ 3.40
Diluted earnings per common share:
Net income	$ 24,283	$ 24,119	$ 24,348	$ 22,983	$ 24,592	$ 22,776	$ 19,670	$ 17,299	$ 95,733	$ 84,337	$ 87,047
Add: Dilutive effect of assumed exercises of stock options and awards (in shares)									144,111	104,699	170,489
Weighted Average Number of Shares Outstanding, Diluted, Total									25,620,105	25,573,941	25,758,893
Diluted earnings per common share (in USD per share)	$ 0.95	$ 0.94	$ 0.95	$ 0.90	$ 0.97	$ 0.89	$ 0.77	$ 0.67	$ 3.74	$ 3.30	$ 3.38
Number of antidilutive stock options									0	0	0