Defined Benefit Pension and Other Postretirement Plans - Components of Net Periodic Pension Benefit (Details) - Pension Plan - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Defined Benefit Plan Disclosure
Service cost	$ 2	$ 4	$ 7	$ 12
Interest cost	9	6	26	19
Expected return on plan assets	(11)	(12)	(34)	(37)
Amortization of:
Actuarial (gain) loss	(1)	2	(2)	6
Net benefit	$ (1)	$ 0	$ (3)	$ 0