Retirement Plans - Schedule of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Retirement Benefits [Abstract]
Service cost	$ 1	$ 1
Interest cost	5	4
Expected return on plan assets	(3)	(3)
Net actuarial and settlement/curtailment (gain) loss	0	8
Net periodic benefit cost	$ 3	$ 10