Retirement Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Retirement Benefits [Abstract]
Service cost	$ 1	$ 1	$ 4	$ 4
Interest cost	4	4	13	14
Expected return on plan assets	(3)	(3)	(10)	(9)
Net periodic benefit cost	$ 2	$ 2	$ 7	$ 9