Stock-Based Compensation Expense (Details2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jul. 01, 2012	Jul. 03, 2011	Jul. 01, 2012	Jul. 03, 2011
Stock-based compensation expense
Stock-based compensation expense	$ 1,989	$ 1,957	$ 5,303	$ 4,309
Product cost of revenue [Member]
Stock-based compensation expense
Stock-based compensation expense	135	105	375	270
Service cost of revenue [Member]
Stock-based compensation expense
Stock-based compensation expense	40	39	108	109
Research, development and engineering [Member]
Stock-based compensation expense
Stock-based compensation expense	483	529	1,350	1,338
Selling, general, and administrative [Member]
Stock-based compensation expense
Stock-based compensation expense	$ 1,331	$ 1,284	$ 3,470	$ 2,592