EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Basic earnings per share:
Net income	$ 12,363		$ 10,903
Weighted-average common shares	30,239,000		28,754,000
Basic earnings per share	$ 0.41		$ 0.38
Diluted earnings per share:
Net income	$ 12,363		$ 10,903
Weighted-average common shares	30,239,000		28,754,000
Effect of dilutive securities:
Employee stock plans	928,000	[1]	1,029,000	[1]
Diluted weighted-average common shares	31,167,000	[1]	29,783,000	[1]
Diluted earnings per share	$ 0.40	[1]	$ 0.37	[1]
Antidilutive shares attributable to stock-based awards outstanding excluded from computation of diluted earnings per share			281,973

[1] The Company includes the shares underlying performance-based awards in the calculation of diluted earnings per share if the performance conditions have been satisfied as of the end of the reporting period and excludes such shares when the necessary conditions have not been met. The Company has excluded the shares underlying the 2014 and 2013 awards in the 2014 and 2013 calculation, respectively, as those shares were not contingently issuable as of the end of the period.