Employee Retirement Plans - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Defined Benefit Plan Disclosure [Line Items]
ABO	$ 24	$ 21
Fair value of plan assets	22	18
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Contribution made to Pension Plan	19	19
Defined benefit plan, benefit obligation	707	623	$ 633
Supplemental Employee Retirement Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, benefit obligation	40	34
Consolidated balance sheets	31	26
U.S. | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Contribution made to Pension Plan	$ 18	$ 18	$ 14