EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net income	$ 51,145	$ 53,882	$ 54,961	$ 103,105
Denominator:
Weighted average basic shares (in shares)	50,665,359	52,863,202	50,801,777	48,381,338
Dilutive potential common shares (in shares)	19,000	191,000	30,000	287,000
Weighted average fully diluted shares (in shares)	50,684,493	53,054,368	50,832,085	48,668,460
Earnings per share:
Basic (in dollars per share)	$ 1.01	$ 1.02	$ 1.08	$ 2.13
Diluted (in dollars per share)	$ 1.01	$ 1.02	$ 1.08	$ 2.12
Outstanding common stock equivalents having no dilutive effect (in shares)	29,000	1,000	18,000	1,000