Defined Benefit Pension and Other Postretirement Plans - Components of Net Periodic Pension Cost (Details) - Pension Plan - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure
Service cost	$ 2	$ 4
Interest cost	9	6
Expected return on plan assets	(11)	(12)
Amortization of:
Actuarial (gain) loss	(1)	2
Net benefit	$ (1)	$ 0