Balance Sheet Components - Schedule of Allowance for Sales Returns (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	$ (17,739)
Ending balance	(21,897)	$ (17,739)
Allowance for Sales Returns
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	(6,907)	(6,916)
Charged to revenue	(17,396)	(19,089)
Utilization of sales return/incentive reserve	16,968	19,098
Ending balance	$ (7,335)	$ (6,907)