Net Loss per Share - Additional Information (Details) shares in Millions |
3 Months Ended | |
|---|---|---|
|
Apr. 30, 2019
$ / shares
shares
|
Jul. 31, 2018
$ / shares
|
|
| Class of Stock [Line Items] | ||
| Shares issuable upon conversion (in shares) | shares | 4.4 | |
| Initial conversion price (in dollars per share) | $ 68.15 | $ 68.15 |
| Average market price (in dollars per share) | $ 122.10 | |
| Class A Common Stock | ||
| Class of Stock [Line Items] | ||
| Number of votes per share | 1 | |
| Class B Common Stock | ||
| Class of Stock [Line Items] | ||
| Number of votes per share | 10 |