EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Numerator for common earnings per share:
Net income	$ 24,430	$ 19,231	$ 48,329	$ 33,945
Numerator for basic and diluted earnings per share	$ 24,430	$ 19,231	$ 48,329	$ 33,945
Denominator for basic earnings per share:
Weighted average common shares outstanding (in shares)	50,211	48,584	49,688	48,237
Effect of dilutive securities (in shares):
Stock options, RSUs and performance-based awards (in shares)	3,060	3,333	3,115	3,224
Denominator for diluted earnings per share (in shares)	53,271	51,917	52,803	51,461
Net income per share:
Basic (in dollars per share)	$ 0.49	$ 0.40	$ 0.97	$ 0.70
Diluted (in dollars per share)	$ 0.46	$ 0.37	$ 0.92	$ 0.66
Anti-dilutive options not included in the calculation (in shares)	2,396	2,105	2,307	1,113