v3.25.2
Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Long-term Debt (Details) - USD ($)
$ in Millions
Jun. 30, 2025
Sep. 30, 2024
Jun. 30, 2024
Carrying amount      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Long-term debt $ 6,644 $ 6,733 $ 6,633
Estimated fair value      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Long-term debt $ 6,743 $ 6,663 $ 6,312