Segment Information - Schedule of Long-Lived Assets and Revenue by Geographical Areas (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Revenues	$ 6,707	$ 6,426	$ 6,037
Long-lived Assets	651	706
United States
Segment Reporting Information [Line Items]
Revenues	2,874	2,870	2,766
Long-lived Assets	450	460
United Kingdom
Segment Reporting Information [Line Items]
Revenues	857	774	726
Long-lived Assets	34	39
Germany
Segment Reporting Information [Line Items]
Revenues	515	513	535
Long-lived Assets	46	99
All other territories
Segment Reporting Information [Line Items]
Revenues	2,461	2,269	$ 2,010
Long-lived Assets	$ 121	$ 108