Convertible Preferred Stock and Stockholders’ Equity (Deficit) - Stock-Based Compensation Expense Narrative (Details) $ in Millions |
9 Months Ended |
|---|---|
|
Sep. 30, 2019
USD ($)
| |
| Equity [Abstract] | |
| Unrecognized compensation cost related to outstanding employee options | $ 3.1 |
| Unrecognized compensation cost related to outstanding employee options, period for recognition | 2 years 4 months 24 days |