Equity and Stock Based Compensation Plans (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 30, 2013	Mar. 31, 2012
Stock-based compensation expense for all share-based payment awards
Total stock-based compensation expense	$ 1,457	$ 1,461
Cost of products [Member]
Stock-based compensation expense for all share-based payment awards
Total stock-based compensation expense	45	57
Cost of service [Member]
Stock-based compensation expense for all share-based payment awards
Total stock-based compensation expense	59	58
Research and development [Member]
Stock-based compensation expense for all share-based payment awards
Total stock-based compensation expense	317	319
Selling [Member]
Stock-based compensation expense for all share-based payment awards
Total stock-based compensation expense	440	441
General and administrative [Member]
Stock-based compensation expense for all share-based payment awards
Total stock-based compensation expense	$ 596	$ 586