EARNINGS PER SHARE (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Numerator for earnings per share:
Net income	$ 17,364	$ 12,680
Net income attributable to common stockholders, basic and diluted earnings per shares	$ 17,364	$ 12,680
Denominator for basic earnings per share:
Weighted average common shares outstanding (in shares)	46,797	44,812
Effect of dilutive securities (in shares):
Stock options	2,410	2,834
Denominator for diluted earnings per share (in shares)	49,207	47,646
Net income per share:
Basic (in dollars per share)	$ 0.37	$ 0.28
Diluted (in dollars per share)	$ 0.35	$ 0.27
Anti-dilutive options not included in the calculation (in shares)	1,271	1,373