Stockholders' Equity (Deficit) - Convertible Preferred Stock Warrants - Additional Information (Details) - shares |
Dec. 31, 2018 |
Dec. 31, 2017 |
Oct. 02, 2017 |
Oct. 01, 2017 |
|---|---|---|---|---|
| Class Of Warrant Or Right [Line Items] | ||||
| Preferred stock, shares outstanding | 0 | 0 | ||
| Class B Common Stock | ||||
| Class Of Warrant Or Right [Line Items] | ||||
| Outstanding warrants to purchase | 0 | 200,000 | ||
| Warrants exercised | 1,900,000 | |||
| Warrants cancelled | 100,000 | |||
| Warrants issued | 1,800,000 | |||
| Initial Public Offering | Class B Common Stock | ||||
| Class Of Warrant Or Right [Line Items] | ||||
| Outstanding warrants to purchase | 2,200,000 | |||
| Convertible Preferred Stock Warrants | ||||
| Class Of Warrant Or Right [Line Items] | ||||
| Preferred stock, shares outstanding | 2,200,000 |