Income Taxes (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Mar. 31, 2025 |
Mar. 31, 2024 |
Mar. 31, 2025 |
Mar. 31, 2024 |
|
| Income Tax Disclosure [Abstract] | ||||
| Effective income tax rate reconciliation, percent (in percent) | 16.00% | 15.00% | 17.00% | 17.00% |
| Recognized tax expense (benefit) | $ (222) | $ (184) | $ (222) | $ (184) |
| Tax expense related to resolution of tax matter | 71 | 71 | ||
| Unrecognized tax benefits, period increase, gross | 246 | 339 | ||
| Unrecognized tax benefits, period increase, net | $ 88 | $ 100 | ||