EARNINGS PER SHARE (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Numerator for common earnings per share:
Net income	$ 19,040	$ 16,437	$ 51,218	$ 43,235
Numerator for basic and diluted earnings per share	$ 19,040	$ 16,437	$ 51,218	$ 43,235
Denominator for basic earnings per share:
Weighted average common shares outstanding (in shares)	47,315	46,162	47,058	45,492
Effect of dilutive securities (in shares):
Stock options, RSUs and performance-based awards (in shares)	2,514	2,558	2,472	2,628
Denominator for diluted earnings per share (in shares)	49,829	48,720	49,530	48,120
Net income per share:
Basic (in dollars per share)	$ 0.40	$ 0.36	$ 1.09	$ 0.95
Diluted (in dollars per share)	$ 0.38	$ 0.34	$ 1.03	$ 0.90
Anti-dilutive options not included in the calculation (in shares)	2,691	1,873	2,152	1,399