Segment Information - Schedule of Long-Lived Assets and Revenue by Geographical Areas (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting Information [Line Items]
Revenues	$ 6,426	$ 6,037	$ 5,919
Long-lived Assets	706	703
United States
Segment Reporting Information [Line Items]
Revenues	2,870	2,766	2,744
Long-lived Assets	460	473
United Kingdom
Segment Reporting Information [Line Items]
Revenues	774	726	734
Long-lived Assets	39	39
Germany
Segment Reporting Information [Line Items]
Revenues	513	535	613
Long-lived Assets	99	98
All other territories
Segment Reporting Information [Line Items]
Revenues	2,269	2,010	$ 1,828
Long-lived Assets	$ 108	$ 93