Stockholders' Equity - Schedule of As-Converted Class B Common Stock (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions |
3 Months Ended | |
|---|---|---|
Dec. 31, 2021 |
Dec. 31, 2020 |
|
| Stockholders' Equity Note [Abstract] | ||
| Reduction in equivalent number of as-converted shares of class A common stock (in shares) | 1 | |
| Effective price per share (in dollars per share) | $ 217.61 | |
| Deposits under the U.S. retrospective responsibility plan | $ 250 | $ 0 |