EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Numerator for basic and diluted earnings per share:
Net income	$ 26,174	$ 22,873	$ 74,503	$ 56,818
Numerator for basic and diluted earnings per share	$ 26,174	$ 22,873	$ 74,503	$ 56,818
Denominator for basic and diluted earnings per share:
Weighted average common shares outstanding (in shares)	51,131	49,043	50,172	48,506
Effect of dilutive securities (in shares):
Stock options, RSUs and restricted stock awards (in shares)	2,733	3,301	2,987	3,249
Denominator for diluted earnings per share (in shares)	53,864	52,344	53,159	51,755
Net income per share:
Basic (in dollars per share)	$ 0.51	$ 0.47	$ 1.48	$ 1.17
Diluted (in dollars per share)	$ 0.49	$ 0.44	$ 1.40	$ 1.10
Anti-dilutive options not included in the calculation (in shares)	2,357	2,143	2,324	1,456