Summary of Significant Accounting Policies - Total Stock-Based Compensation Expense (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 27, 2015	Jun. 28, 2014	Jun. 27, 2015	Jun. 28, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 533,000	$ 170,000	$ 1,085,000	$ 356,000
Cost of Revenue [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	1,000		1,000
Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	78,000	43,000	169,000	91,000
Selling, general and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 454,000	$ 127,000	$ 915,000	$ 265,000