Pension & Postretirement Plans - Schedule of Pension and Postretirement Plan Expenses (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Retirement Benefits [Abstract]
Service cost	$ 9	$ 12
Interest cost	55	54
Expected return on plan assets	(74)	(71)
Net amortization	(14)	(20)
Total	$ (24)	$ (25)