EARNINGS PER SHARE - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
EARNINGS PER SHARE
Average common shares outstanding	13,716	14,221
Net income and net income available to common stockholders	$ 18,868	$ 14,868
Per common share amount	$ 1.38	$ 1.05
Average common shares outstanding	13,716	14,221
Net effect of dilutive stock options - based on the treasury stock method using average market price	112	78
Diluted common shares	13,828	14,299
Net income and net income available to common stockholders	$ 18,868	$ 14,868
Per common share amount	$ 1.36	$ 1.04