Balance Sheet Components - Schedule of Allowance for Sales Incentives (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance, beginning of period	$ (21,897)
Balance, end of period	(13,105)	$ (21,897)
Allowance for Sales Incentives
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance, beginning of period	(13,750)	(10,442)
Charged to revenue	(26,947)	(50,958)
Utilization of sales return/incentive reserve	32,319	47,650
Balance, end of period	$ (8,378)	$ (13,750)