Balance Sheet Components - Product Sales Rebate and Returns Reserve (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Sales Return Reserve [Roll Forward]
Balance at the beginning of year	$ 1,317	$ 566	$ 2,031
Additions charged against revenue	17,371	5,122	818
Consumption	(11,265)	(4,371)	(2,283)
Balance at the end of year	$ 7,423	$ 1,317	$ 566