Balance Sheet Components - Schedule of Accounts Receivable, Net of allowances (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Valuation And Qualifying Accounts Disclosure [Line Items]
Gross accounts receivable	$ 134,564	$ 138,292
Allowance for accounts receivable	(10,952)	(17,739)
Total Accounts Receivable—net of allowances	123,612	120,553
Allowance for Sales Returns
Valuation And Qualifying Accounts Disclosure [Line Items]
Allowance for accounts receivable	(4,504)	(6,907)	$ (6,916)
Allowance for Sales Incentives
Valuation And Qualifying Accounts Disclosure [Line Items]
Allowance for accounts receivable	(6,153)	(10,442)	$ (8,503)
Other Allowances
Valuation And Qualifying Accounts Disclosure [Line Items]
Allowance for accounts receivable	$ (295)	$ (390)