Earnings Per Share (Details) (USD $) In Thousands, except Share data	3 Months Ended		6 Months Ended
	Jul. 02, 2011	Jul. 03, 2010	Jul. 02, 2011	Jul. 03, 2010
Earnings Per Share
Net income	$ 13,372	$ 21,047	$ 11,412	$ 42,126
Shares used in computing basic earnings per share (in shares)	44,602,000	45,387,000	44,435,000	45,602,000
Effect of dilutive securities:
Stock options and awards (in shares)	1,349,000	1,984,000	1,563,000	2,047,000
Shares used in computing diluted earnings per share (in shares)	45,951,000	47,371,000	45,998,000	47,649,000
Earnings per share:
Basic (in dollars per share)	$ 0.30	$ 0.46	$ 0.26	$ 0.92
Diluted (in dollars per share)	$ 0.29	$ 0.44	$ 0.25	$ 0.88
Weighted-average dilutive potential shares excluded from computation of earning per share (in shares)	500,000	600,000	400,000	600,000