Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 27, 2014	Sep. 28, 2013	Sep. 27, 2014	Sep. 28, 2013
Earnings Per Share
Net income	$ 5,608	$ 6,531	$ 27,997	$ 39,177
Shares used in computing basic earnings per share	43,112,000	42,684,000	43,218,000	42,477,000
Effect of dilutive securities:
Stock options and other stock-based awards (in shares)	703,000	1,238,000	812,000	960,000
Shares used in computing diluted earnings per share	43,815,000	43,922,000	44,030,000	43,437,000
Earnings per share:
Basic (in dollars per share)	$ 0.13	$ 0.15	$ 0.65	$ 0.92
Diluted (in dollars per share)	$ 0.13	$ 0.15	$ 0.64	$ 0.90
Shares excluded from computation of diluted earning per share	100,000	500,000	100,000	400,000