Goodwill and Other Intangible Assets - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Goodwill [Line Items]
Goodwill	$ 2,164,000,000	$ 2,164,000,000	$ 2,094,000,000	$ 2,057,000,000
Impairment		0
Amortization of intangibles		47,000,000	50,000,000	52,000,000
Anticipated amortization expense, 2025	47,000,000	47,000,000
Anticipated amortization expense, 2026	46,000,000	46,000,000
Anticipated amortization expense, 2027	40,000,000	40,000,000
Anticipated amortization expense, 2028	32,000,000	32,000,000
Anticipated amortization expense, 2029	32,000,000	32,000,000
EMEA
Goodwill [Line Items]
Goodwill	$ 341,000,000	$ 341,000,000	$ 317,000,000	$ 295,000,000
Volkswagen Group | Net sales | Customer concentration risk
Goodwill [Line Items]
Concentration risk (as percent)		13.00%	11.00%
Valuation, Income Approach | Minimum | Measurement Input, Cap Rate | Significant Unobservable Inputs (Level 3)
Goodwill [Line Items]
Reporting unit, measurement input	15.50%
Valuation, Income Approach | Maximum | Measurement Input, Cap Rate | Significant Unobservable Inputs (Level 3)
Goodwill [Line Items]
Reporting unit, measurement input	18.50%