Earnings Per Share - Schedule of Weighted Average Number of Shares (Detail) - shares shares in Millions |
12 Months Ended | ||
|---|---|---|---|
Sep. 30, 2024 |
Sep. 30, 2023 |
Sep. 30, 2022 |
|
| Class B-1 common stock | |||
| Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items] | |||
| Weighted-average as-converted common stock used in income allocation (in shares) | 235 | 392 | 397 |
| Class B-2 common stock | |||
| Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items] | |||
| Weighted-average as-converted common stock used in income allocation (in shares) | 77 | 0 | 0 |
| Class C common stock | |||
| Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items] | |||
| Weighted-average as-converted common stock used in income allocation (in shares) | 64 | 39 | 40 |
| Participating securities | |||
| Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items] | |||
| Weighted-average as-converted common stock used in income allocation (in shares) | 29 | 34 | 47 |