EARNINGS PER SHARE - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
EARNINGS PER SHARE
Average common shares outstanding	13,534	14,053	13,652	14,119
Net income and net income available to common stockholders	$ 20,364	$ 13,454	$ 59,346	$ 41,525
Per common share amount	$ 1.50	$ 0.96	$ 4.35	$ 2.94
Average common shares outstanding	13,534	14,053	13,652	14,119
Net effect of dilutive stock options - based on the treasury stock method using average market price	92	32	92	46
Diluted common shares	13,626	14,085	13,744	14,165
Net income and net income available to common stockholders	$ 20,364	$ 13,454	$ 59,346	$ 41,525
Per common share amount	$ 1.49	$ 0.96	$ 4.32	$ 2.93