Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 29, 2013	Jun. 30, 2012	Jun. 29, 2013	Jun. 30, 2012
Earnings Per Share
Net income	$ 12,612	$ 20,509	$ 32,646	$ 34,829
Shares used in computing basic earnings per share	42,552,000	42,655,000	42,370,000	42,556,000
Effect of dilutive securities:
Stock options and other stock-based awards (in shares)	717,000	768,000	821,000	1,081,000
Shares used in computing diluted earnings per share	43,269,000	43,423,000	43,191,000	43,637,000
Earnings per share:
Basic (in dollars per share)	$ 0.30	$ 0.48	$ 0.77	$ 0.82
Diluted (in dollars per share)	$ 0.29	$ 0.47	$ 0.76	$ 0.80
Shares excluded from computation of diluted earning per share	500,000	1,200,000	400,000	800,000