Pension and Postretirement Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	$ 15	$ 59	$ 23	$ (17)
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1	1	2	1
Expected return on plan assets	(2)	(2)	(4)	(4)
Amortization of prior service credit	(1)	(1)	(2)	(2)
Net periodic benefit cost (credit)	(2)	(2)	(4)	(5)
United States | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost	20	11	41	21
Expected return on plan assets	(33)	(41)	(67)	(82)
Net actuarial loss (gain)	15	60	23	18
Settlement loss	1	2	1	1
Net periodic benefit cost (credit)	3	32	(2)	(42)
Foreign Plan | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	4	5	7	11
Interest cost	17	10	33	20
Expected return on plan assets	(19)	(21)	(37)	(42)
Net actuarial loss (gain)	0	(1)	0	(1)
Settlement loss	0	8	0	8
Net periodic benefit cost (credit)	$ 2	$ 1	$ 3	$ (4)