Pension and Retirement Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Pension Plan | United States
Components of Net Periodic Benefit Cost (Credit):
Service cost	$ 0	$ 0	$ 0
Interest cost	65	79	78
Expected return on plan assets	(98)	(120)	(131)
Net actuarial (gain) loss	48	(9)	28
Settlement loss	0	0	1
Amortization of prior service credit	0	0	0
Other	0	0	0
Net periodic benefit cost (credit)	$ 15	$ (50)	$ (24)
Expense Assumptions:
Discount rate	4.60%	5.48%	5.08%
Expected return on plan assets	6.50%	8.50%	8.25%
Interest crediting rate	6.00%	6.00%
Pension Plan | Foreign Plan
Components of Net Periodic Benefit Cost (Credit):
Service cost	$ 17	$ 17	$ 16
Interest cost	64	69	68
Expected return on plan assets	(77)	(72)	(77)
Net actuarial (gain) loss	(2)	22	86
Settlement loss	(3)	0	6
Amortization of prior service credit	0	0	0
Other	1	1	0
Net periodic benefit cost (credit)	$ 0	$ 37	$ 99
Expense Assumptions:
Discount rate	4.35%	4.72%	4.36%
Expected return on plan assets	5.44%	5.26%	5.02%
Rate of compensation increase	3.01%	2.90%	3.00%
Interest crediting rate	1.58%	1.63%	1.69%
Postretirement Benefits
Components of Net Periodic Benefit Cost (Credit):
Service cost	$ 0	$ 0	$ 0
Interest cost	3	4	4
Expected return on plan assets	(11)	(9)	(9)
Net actuarial (gain) loss	(14)	(14)	(5)
Settlement loss	0	0	0
Amortization of prior service credit	(5)	(5)	(4)
Other	0	0	0
Net periodic benefit cost (credit)	$ (27)	$ (24)	$ (14)
Expense Assumptions:
Discount rate	4.50%	5.42%	4.92%
Expected return on plan assets	6.64%	6.62%	6.64%