EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Numerator for earnings per share:
Net income	$ 14,814	$ 14,118	$ 32,178	$ 26,798
Net income attributable to common stockholders, basic and diluted earnings per shares	$ 14,814	$ 14,118	$ 32,178	$ 26,798
Denominator for basic earnings per share:
Weighted average common shares outstanding (in shares)	47,068,000	45,486,000	46,933,000	45,151,000
Effect of dilutive securities (in shares):
Stock options, RSUs and performance-based awards	2,491,000	2,491,000	2,451,000	2,662,000
Denominator for diluted earnings per share (in shares)	49,559,000	47,977,000	49,384,000	47,813,000
Net income per share:
Basic (in dollars per share)	$ 0.31	$ 0.31	$ 0.69	$ 0.59
Diluted (in dollars per share)	$ 0.30	$ 0.29	$ 0.65	$ 0.56
Anti-dilutive options not included in the calculation (in shares)	2,493	950	1,882	1,162