EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Numerator for basic and diluted earnings per share:
Net income	$ 23,641	$ 23,899
Numerator for basic and diluted earnings per share	$ 23,641	$ 23,899
Denominator:
Weighted average common shares outstanding (in shares)	50,958	49,714
Effect of dilutive securities (in shares):
Stock options, RSUs and restricted stock awards (in shares)	2,931	3,169
Denominator for diluted earnings per share (in shares)	53,889	52,883
Net income per share:
Basic (in dollars per share)	$ 0.46	$ 0.48
Diluted (in dollars per share)	$ 0.44	$ 0.45
Anti-dilutive options not included in the calculation (in shares)	2,272	2,218