Benefit Plans - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Defined Benefit Plan Disclosure [Line Items]
Percent of total assets domestic plans	64.00%
Cost of the savings incentive plan	$ 262	$ 195	$ 156
Fixed Income Funds
Defined Benefit Plan Disclosure [Line Items]
Company's target allocation percentage for asset mix	45.00%
Diversified
Defined Benefit Plan Disclosure [Line Items]
Company's target allocation percentage for asset mix	22.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Company's target allocation percentage for asset mix	33.00%
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	$ 2,466	2,557	2,129
Pension plan projected benefit obligations	2,837	2,913	$ 2,617
Employer contribution	46	200
International plans | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	895	880
Pension plan projected benefit obligations	$ 987	992
Percent of total plan assets foreign plans	36.00%
International plans | Pension Plans | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	$ 177	196
United States | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	1,572	1,676
Employer contribution		150
United States | Pension Plans | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	520	582
United States | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan projected benefit obligations	$ 79	$ 94