Defined Benefit Pension and Other Postretirement Plans - Components of Net Periodic Pension Cost (Details) - Pension Benefits - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Defined Benefit Plan Disclosure
Service cost	$ 4	$ 3	$ 8	$ 6
Interest cost	7	6	13	11
Expected return on assets	(13)	(10)	(25)	(20)
Amortization of:
Actuarial loss	2	3	4	7
Net cost	$ 0	$ 2	$ 0	$ 4