Defined Benefit Pension and Other Postretirement Plans - Components of Net Periodic Pension Cost (Details) - Pension Plan - 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
Service cost	$ 3	$ 4	$ 5	$ 8
Interest cost	8	7	17	13
Expected return on plan assets	(12)	(13)	(23)	(25)
Amortization of:
Actuarial (gain) loss	0	2	(1)	4
Net benefit	$ (1)	$ 0	$ (2)	$ 0