Fair Value Measurements - Summary of Financial Instruments Subject to Recurring Fair Value Measurements (Parenthetical) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Sep. 30, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted Investments	$ 295	$ 290
Restricted Investments, Current	73	77
Asbestos Trust [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted Investments, Current	36	37
Available-for-sale securities, fair value	248	243
Environmental Trust [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted Investments, Current	37	40
Available-for-sale securities, fair value	$ 120	$ 124