Share-Based Compensation Expense Recorded In Income from Continuing Operations in Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2016	Jul. 03, 2015	Jul. 01, 2016	Jul. 03, 2015
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 1,055	$ 659	$ 2,397	$ 2,212
Selling, general and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	955	832	2,198	2,316
Research and development and engineering
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	39	31	64	80
Cost of Revenue
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 61	73	$ 135	137
Restructuring, acquisition and divestiture related costs
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense, adjustment		$ (277)		$ (321)