Stockholders' Equity - Effect of VE Territory Covered Losses Through Conversion Rate Adjustments (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions |
6 Months Ended | |
|---|---|---|
Mar. 31, 2025 |
Mar. 31, 2024 |
|
| Conversion of Stock [Line Items] | ||
| Reduction in equivalent number of class A common stock (in shares) | 1 | 0 |
| Effective price per share (in dollars per share) | $ 346.79 | $ 0 |
| Deposits into the U.S. litigation escrow account | $ 375 | $ 0 |
| Recovery through conversion rate adjustment | $ 0 | $ 0 |
| Series B preferred stock | ||
| Conversion of Stock [Line Items] | ||
| Reduction in equivalent number of class A common stock (in shares) | 0 | 0 |
| Effective price per share (in dollars per share) | $ 312.39 | $ 254.32 |
| Recovery through conversion rate adjustment | $ 5 | $ 22 |
| Series C preferred stock | ||
| Conversion of Stock [Line Items] | ||
| Reduction in equivalent number of class A common stock (in shares) | 0 | 0 |
| Effective price per share (in dollars per share) | $ 312.39 | $ 254.32 |
| Recovery through conversion rate adjustment | $ 3 | $ 3 |