Effect of Recording Equity-Based Compensation (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Oct. 01, 2016	Sep. 30, 2017	Oct. 01, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity-based compensation	$ 1,148	$ 905	$ 3,012	$ 2,896
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity-based compensation	350	211	808	696
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity-based compensation	731	543	1,943	1,657
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity-based compensation	$ 67	$ 151	$ 261	$ 543