EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Basic and Diluted Earnings:
Net income	$ 29,572	$ 27,074	$ 21,554	$ 3,953	$ 17,335	$ 19,792	$ 18,610	$ 18,817	$ 82,153	$ 74,554	$ 74,138
Basic weighted-average shares outstanding (in shares)									33,201	33,747	34,951
Add: Stock options (in shares)									80	148	165
Diluted weighted-average shares outstanding (in shares)									33,281	33,895	35,116
Basic earnings per share:
Earnings per common share - basic (in dollars per share)	$ 0.89	$ 0.82	$ 0.65	$ 0.12	$ 0.51	$ 0.59	$ 0.55	$ 0.56	$ 2.47	$ 2.21	$ 2.12
Diluted earnings per share:
Earnings per common share - diluted (in dollars per share)	$ 0.89	$ 0.82	$ 0.65	$ 0.12	$ 0.51	$ 0.58	$ 0.55	$ 0.56	$ 2.47	$ 2.20	$ 2.11
Antidilutive securities from non-qualified stock options excluded from calculating earnings
Number of antidilutive options (in shares)									808	521	356