Balance Sheet Components - Accrued Expenses (Details) - USD ($) $ in Thousands |
Sep. 30, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Organization, Consolidation and Presentation of Financial Statements [Abstract] | ||
| Accrued compensation | $ 22,545 | $ 18,568 |
| Accrued income and other taxes payable | 4,891 | 3,492 |
| Accrued other current liabilities | 3,979 | 4,454 |
| Accrued expenses | $ 31,415 | $ 26,514 |