Net Loss Per Share - Numerators and Denominators of Basic and Diluted Net Income (Loss) Per Share Computations (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2018	Sep. 29, 2017	Sep. 28, 2018	Sep. 29, 2017
Numerator:
Net loss	$ (7,758)	$ (15,583)	$ (24,365)	$ (71,110)
Denominator:
Basic and diluted	86,321	81,445	85,188	80,618
Net loss per share:
Basic and diluted	$ (0.09)	$ (0.19)	$ (0.29)	$ (0.88)