EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Numerator for common earnings per share:
Net income	$ 19,231	$ 14,814	$ 33,945	$ 32,178
Numerator for basic and diluted earnings per share	$ 19,231	$ 14,814	$ 33,945	$ 32,178
Denominator for basic earnings per share:
Weighted average common shares outstanding (in shares)	48,584	47,068	48,237	46,933
Effect of dilutive securities (in shares):
Stock options, RSUs and performance-based awards (in shares)	3,333	2,491	3,224	2,451
Denominator for diluted earnings per share (in shares)	51,917	49,559	51,461	49,384
Net income per share:
Basic (in dollars per share)	$ 0.40	$ 0.31	$ 0.70	$ 0.69
Diluted (in dollars per share)	$ 0.37	$ 0.30	$ 0.66	$ 0.65
Anti-dilutive options not included in the calculation (in shares)	2,105	2,493	1,113	1,882