Convertible Preferred Stock and Stockholders’ Equity (Deficit) - Employee Stock Purchase Plan Narrative (Details) - shares |
9 Months Ended | |
|---|---|---|
Sep. 30, 2019 |
Aug. 31, 2018 |
|
| Subsidiary, Sale of Stock [Line Items] | ||
| Common stock initially reserved for future issuance (shares) | 6,374,148 | |
| Number of common stock purchased under plan (shares) | 66,155 | |
| 2018 Employee Stock Purchase Plan | ||
| Subsidiary, Sale of Stock [Line Items] | ||
| Common stock initially reserved for future issuance (shares) | 175,000 | |
| Incremental rate at which the shares reserved for issuance increase | 1.00% | |
| 2018 Employee Stock Purchase Plan | Maximum | ||
| Subsidiary, Sale of Stock [Line Items] | ||
| Common stock initially reserved for future issuance (shares) | 220,000 |