Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 28, 2014	Jun. 29, 2013	Jun. 28, 2014	Jun. 29, 2013
Earnings Per Share
Net income	$ 14,279	$ 12,612	$ 22,389	$ 32,646
Shares used in computing basic earnings per share	43,462,000	42,552,000	43,271,000	42,370,000
Effect of dilutive securities:
Stock options and other stock-based awards (in shares)	756,000	717,000	866,000	821,000
Shares used in computing diluted earnings per share	44,218,000	43,269,000	44,137,000	43,191,000
Earnings per share:
Basic (in dollars per share)	$ 0.33	$ 0.30	$ 0.52	$ 0.77
Diluted (in dollars per share)	$ 0.32	$ 0.29	$ 0.51	$ 0.76
Shares excluded from computation of diluted earning per share	100,000	500,000	200,000	400,000