Employee Retirement Plans - Net Periodic Pension Costs (Details) - Pension Benefits - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 16	$ 12	$ 11
Interest cost	26	22	23
Expected return on assets	(50)	(40)	(38)
Curtailment gain	0	0	(1)
Amortization of:
Prior service cost	0	0	1
Actuarial loss	7	14	15
Net benefit (income) cost	$ (1)	$ 8	$ 11