Balance Sheet Components - Schedule of Accounts Receivable, Net of Allowances (Details) - USD ($) $ in Thousands |
Jun. 30, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|---|
| Valuation And Qualifying Accounts Disclosure [Line Items] | |||
| Gross accounts receivable | $ 218,296 | $ 204,975 | |
| Allowance for accounts receivable | (14,259) | (21,897) | |
| Total Accounts Receivable—net of allowances | 204,037 | 183,078 | |
| Allowance for Sales Returns | |||
| Valuation And Qualifying Accounts Disclosure [Line Items] | |||
| Allowance for accounts receivable | (5,250) | (7,335) | $ (6,907) |
| Allowance for Sales Incentives | |||
| Valuation And Qualifying Accounts Disclosure [Line Items] | |||
| Allowance for accounts receivable | (8,583) | (13,750) | $ (10,442) |
| Other Allowances | |||
| Valuation And Qualifying Accounts Disclosure [Line Items] | |||
| Allowance for accounts receivable | $ (426) | $ (812) |