Redeemable Convertible Preferred Stock, Common Stock, and Equity (Deficit) - Stock-Based Compensation Expense (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2019 |
Sep. 30, 2018 |
Sep. 30, 2019 |
Sep. 30, 2018 |
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Share-based compensation expense | $ 401 | $ 64 | $ 4,353 | $ 147 |
| Operations and support | ||||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Share-based compensation expense | 26 | 4 | 431 | 11 |
| Sales and marketing | ||||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Share-based compensation expense | 16 | 2 | 229 | 6 |
| Research and development | ||||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Share-based compensation expense | 262 | 49 | 2,822 | 60 |
| General and administrative | ||||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Share-based compensation expense | $ 97 | $ 9 | $ 871 | $ 70 |