Balance Sheet Components - Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Apr. 01, 2017	Oct. 01, 2016
Net Unrealized Loss
Beginning balance	$ 17,000
Ending balance	(49,000)
Income Tax Provision
Tax impact on unrealized gains or losses	0	$ 0
Reclassifications out of accumulated other comprehensive income	0	$ 0
Accumulated Net Unrealized Investment Gain (Loss)
Net Unrealized Loss
Available-for-sale Securities, Gross Unrealized Loss	(32,000)
Other comprehensive income (loss), before tax	$ (32,000)