Net Income Per Share (Details 2) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 28, 2013	Sep. 29, 2012	Sep. 28, 2013	Sep. 29, 2012
Diluted net income per common share calculation
Net income	$ 18,904	$ 24,255	$ 60,263	$ 70,549
Net income allocated to participating securities				(20)
Net income attributable to common shareholders	$ 18,904	$ 24,255	$ 60,263	$ 70,529
Weighted average number of common shares used to compute basic net income per common share attributable to common shares	57,427	58,762	57,447	58,645
Dilutive effect of share-based compensation plans (in shares)	807	907	953	964
Weighted average number of common shares used to compute diluted net income per common share	58,234	59,669	58,400	59,609
Diluted net income per common share (in dollars per share)	$ 0.32	$ 0.41	$ 1.03	$ 1.18
Options
Potential common share equivalents excluded
Options to purchase shares not included in the computation of diluted income per share because their inclusion would be anti-dilutive	642	640	1,008	509