Stockholders' Equity and Stock-Based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 24, 2016	Sep. 26, 2015	Sep. 24, 2016	Sep. 26, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense related to employee stock options and employee stock purchases	$ 2,000	$ 1,682	$ 5,432	$ 4,664
Cost of products [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense related to employee stock options and employee stock purchases	116	96	273	229
Cost of service [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense related to employee stock options and employee stock purchases	138	104	355	195
Research and development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense related to employee stock options and employee stock purchases	387	300	985	796
Selling [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense related to employee stock options and employee stock purchases	537	511	1,492	1,403
General and administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense related to employee stock options and employee stock purchases	$ 822	$ 671	$ 2,327	$ 2,041