NET INCOME PER COMMON SHARE - Schedule of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net income	$ 36,962	$ 22,818	$ 111,876	$ 39,591
Adjustment for Basic EPS:
Earnings allocated to unvested shareholders	(260)	(242)	(922)	(481)
Adjusted net income	$ 36,702	$ 22,576	$ 110,954	$ 39,110
Denominator:
Weighted average common shares outstanding – Basic	46,980,439	46,869,998	46,947,109	46,841,036
Effect of dilutive shares:
Common stock equivalents arising from stock options and ESPP	249	754	1,142	1,682
Restricted stock awards and units and performance units	33,231	43,801	35,650	51,050
Weighted average common shares outstanding – Diluted	47,013,919	46,914,553	46,983,901	46,893,768
Basic	$ 0.78	$ 0.48	$ 2.36	$ 0.83
Diluted	$ 0.78	$ 0.48	$ 2.36	$ 0.83