Stockholders' Equity - Effect of VE Territory Covered Losses Through Coversion Rate Adjustments (Details) - USD ($) $ / shares in Units, $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2020 |
Jun. 30, 2019 |
Jun. 30, 2020 |
Jun. 30, 2019 |
|
| Conversion of Stock [Line Items] | ||||
| Recovery through conversion rate adjustment | $ 5 | $ 0 | $ 5 | |
| UK&I preferred stock | ||||
| Conversion of Stock [Line Items] | ||||
| Reduction in equivalent number of as-converted shares of class A common stock (in shares) | 0 | 0 | ||
| Effective price per share (in dollars per share) | $ 180.00 | $ 141.32 | ||
| Recovery through conversion rate adjustment | $ 72 | $ 6 | ||
| Europe preferred stock | ||||
| Conversion of Stock [Line Items] | ||||
| Reduction in equivalent number of as-converted shares of class A common stock (in shares) | 1 | 0 | ||
| Effective price per share (in dollars per share) | $ 180.00 | $ 150.26 | ||
| Recovery through conversion rate adjustment | $ 92 | $ 2 | ||