EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data	3 Months Ended				6 Months Ended
	Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011		Jun. 30, 2010
Basic earnings per share:
Net income	$ 10,599		$ 15,587		$ 20,453		$ 27,901
Weighted Average Common Shares	28,938,000		27,844,000		28,784,000		27,658,000
Basic earnings per share	$ 0.37		$ 0.56		$ 0.71		$ 1.01
Diluted earnings per share:
Net income	$ 10,599		$ 15,587		$ 20,453		$ 27,901
Weighted Average Common Shares	28,938,000		27,844,000		28,784,000		27,658,000
Effect of dilutive securities:
Employee stock plans	1,408,000	[1]	1,691,000	[1]	1,487,000	[1]	1,802,000	[1]
Diluted weighted average common shares	30,346,000	[1]	29,535,000	[1]	30,271,000	[1]	29,460,000	[1]
Diluted earnings per share	$ 0.35	[1]	$ 0.53	[1]	$ 0.68	[1]	$ 0.95	[1]
Antidilutive shares attributable to stock-based awards outstanding excluded from computation of diluted earnings per share	262,533		95,793		234,700		68,180

[1] The Company includes the shares underlying performance-based awards in the calculation of diluted earnings per share when they become contingently issuable per ASC 260-10, Earnings per Share and excludes such shares when they are not contingently issuable. The Company has excluded all performance-based awards underlying the fiscal 2011 and 2010 awards as those shares are not contingently issuable as of the end of the period.