Income Tax - Additional Information (Detail) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Income Taxes [Line Items] | ||||
| Net discrete tax expense (benefit) | $ 19 | $ 1 | $ 30 | $ 10 |
| United States Internal Revenue Service (IRS) [Member] | ||||
| Income Taxes [Line Items] | ||||
| Tax years remain subject to examination | 2023 2024 2025 | |||
| State Tax Authorities [Member] | ||||
| Income Taxes [Line Items] | ||||
| Tax years remain subject to examination | 2019 2020 2021 2022 2023 2024 2025 | |||
| Foreign Jurisdictions [Member] | ||||
| Income Taxes [Line Items] | ||||
| Tax years remain subject to examination | 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 | |||