Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jul. 02, 2011	Jun. 30, 2012	Jul. 02, 2011
Earnings Per Share
Net income	$ 20,509	$ 13,372	$ 34,829	$ 11,412
Shares used in computing basic earnings per share	42,655,000	44,602,000	42,556,000	44,435,000
Effect of dilutive securities:
Stock options and other stock-based awards (in shares)	768,000	1,349,000	1,081,000	1,563,000
Shares used in computing diluted earnings per share	43,423,000	45,951,000	43,637,000	45,998,000
Earnings per share:
Basic (in dollars per share)	$ 0.48	$ 0.30	$ 0.82	$ 0.26
Diluted (in dollars per share)	$ 0.47	$ 0.29	$ 0.80	$ 0.25
Shares excluded from computation of diluted earning per share	1,200,000	500,000	800,000	400,000