Net Income Per Share (Details) (USD $) In Thousands, except Share data	3 Months Ended		6 Months Ended
	Jun. 28, 2011	Jun. 29, 2010	Jun. 28, 2011	Jun. 29, 2010
Net Income Per Share
Shares of restricted stock issued to employees were unvested	700,000	600,000	700,000	600,000
Net income per share, basic and diluted
Net income	$ 24,748	$ 19,229	$ 45,204	$ 37,895
Basic weighted average shares outstanding (in shares)	56,554,000	59,238,000	57,517,000	59,261,000
Dilutive effect of stock options and restricted shares (in shares)	2,041,000	1,625,000	2,026,000	1,445,000
Diluted weighted average shares outstanding (in shares)	58,595,000	60,863,000	59,543,000	60,706,000
Basic net income per share (in dollars per share)	$ 0.44	$ 0.32	$ 0.79	$ 0.64
Diluted net income per share (in dollars per share)	$ 0.42	$ 0.32	$ 0.76	$ 0.62
Shares of common stock not included in the diluted calculation due to their anti-dilutive effect (in shares)	2,400,000	3,800,000	2,600,000	5,200,000