Balance Sheet Components - Restructuring (Details) - Employee Severance [Member] $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Oct. 01, 2016 USD ($)	Sep. 30, 2017 USD ($) employee	Oct. 01, 2016 USD ($)
Restructuring Cost and Reserve [Line Items]
Expected number of positions eliminated | employee			110
Number of positions eliminated in the period, percent			6.00%
Severance costs			$ 6,400
Restructuring Reserve [Roll Forward]
Beginning balance	$ 1,022	$ 0	0	$ 0
Restructuring charges	0	0	6,375	0
Cash paid	(359)	0	(4,984)	0
Other - noncash	0	0	(728)	0
Restructuring Reserve	$ 663	$ 0	$ 663	$ 0