NET INCOME PER COMMON SHARE - Schedule of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ 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
Numerator:
Net income	$ 53,902	$ 40,500	$ 815	$ 38,155	$ 26,428	$ 36,962	$ 43,440	$ 31,474	$ 133,372	$ 138,304	$ 58,840
Adjustment for Basic EPS:
Earnings allocated to unvested shareholders									(1,001)	(1,106)	(690)
Adjusted net income									$ 132,371	$ 137,198	$ 58,150
Denominator:
Weighted average common shares outstanding – Basic									47,198,982	46,959,775	46,849,588
Effect of dilutive shares:
Common stock equivalents arising from stock options and ESPP									1,566	1,334	1,956
Restricted stock awards and units and performance units									36,446	34,353	45,222
Weighted average common shares outstanding – Diluted									47,236,994	46,995,462	46,896,766
Basic	$ 1.13	$ 0.85	$ 0.02	$ 0.80	$ 0.56	$ 0.78	$ 0.92	$ 0.66	$ 2.80	$ 2.92	$ 1.24
Diluted	$ 1.13	$ 0.85	$ 0.02	$ 0.80	$ 0.56	$ 0.78	$ 0.92	$ 0.66	$ 2.80	$ 2.92	$ 1.24