Earnings Per Share (Details) (USD $) In Thousands, except Share data	3 Months Ended		9 Months Ended
	Oct. 01, 2011	Oct. 02, 2010	Oct. 01, 2011	Oct. 02, 2010
Earnings Per Share
Net income	$ 11,255	$ 18,233	$ 22,667	$ 60,359
Shares used in computing basic earnings per share (in shares)	42,834,000	44,341,000	43,902,000	45,182,000
Effect of dilutive securities:
Stock options and awards (in shares)	1,085,000	1,668,000	1,403,000	1,921,000
Shares used in computing diluted earnings per share (in shares)	43,919,000	46,009,000	45,305,000	47,103,000
Earnings per share:
Basic (in dollars per share)	$ 0.26	$ 0.41	$ 0.52	$ 1.34
Diluted (in dollars per share)	$ 0.26	$ 0.40	$ 0.50	$ 1.28
Weighted-average dilutive potential shares excluded from computation of earning per share (in shares)	1,400,000	800,000	500,000	700,000