Fair Value Measurements - Recurring Fair Value Measurements (Details) - USD ($) $ in Millions	Sep. 30, 2024	Sep. 30, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]		Other current assets
Derivative Asset, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Other noncurrent assets
Total assets	$ 18	$ 34
Derivative Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other current liabilities	Other current liabilities
Derivative Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other noncurrent liabilities	Other noncurrent liabilities
Total liabilities	$ 41	$ 14
Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]	Other current assets	Other current assets
Derivative asset, current	$ 15	$ 34
Derivative Asset, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other noncurrent assets	Other noncurrent assets
Derivative asset, noncurrent	$ 3
Derivative Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other current liabilities	Other current liabilities
Derivative liability, current	$ 32	$ 8
Derivative liability, noncurrent	9	6
Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	0	0
Total liabilities	0	0
Quoted Prices in Active Markets (Level 1) | Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, current	0	0
Derivative asset, noncurrent	0
Derivative liability, current	0	0
Derivative liability, noncurrent	0	0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	18	34
Total liabilities	41	14
Significant Other Observable Inputs (Level 2) | Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, current	15	34
Derivative asset, noncurrent	3
Derivative liability, current	32	8
Derivative liability, noncurrent	9	6
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	0	0
Total liabilities	0	0
Significant Unobservable Inputs (Level 3) | Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, current	0	0
Derivative asset, noncurrent	0
Derivative liability, current	0	0
Derivative liability, noncurrent	$ 0	$ 0