Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 28, 2013	Sep. 29, 2012	Sep. 28, 2013	Sep. 29, 2012
Earnings Per Share
Net income	$ 6,531	$ 10,024	$ 39,177	$ 44,853
Shares used in computing basic earnings per share	42,684,000	41,735,000	42,477,000	42,279,000
Effect of dilutive securities:
Stock options and other stock-based awards (in shares)	1,238,000	785,000	960,000	982,000
Shares used in computing diluted earnings per share	43,922,000	42,520,000	43,437,000	43,261,000
Earnings per share:
Basic (in dollars per share)	$ 0.15	$ 0.24	$ 0.92	$ 1.06
Diluted (in dollars per share)	$ 0.15	$ 0.24	$ 0.90	$ 1.04
Shares excluded from computation of diluted earning per share	500,000	800,000	400,000	900,000