Fair Value Measurements - Recurring Fair Value Measurements (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets fair value	$ 23	$ 23
Financial liabilities fair value	15	15
Other current assets | Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	8	8
Other current assets | Cross-currency interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	12
Other noncurrent assets | Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	1	2
Other noncurrent assets | Cross-currency interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	1	13
Other noncurrent assets | Interest rate cap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	1
Other current liabilities | Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	12	11
Other noncurrent liabilities | Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	3	2
Other noncurrent liabilities | Equity swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability		2
Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets fair value	0	0
Financial liabilities fair value	0	0
Quoted Prices in Active Markets (Level 1) | Other current assets | Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	0	0
Quoted Prices in Active Markets (Level 1) | Other current assets | Cross-currency interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	0
Quoted Prices in Active Markets (Level 1) | Other noncurrent assets | Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	0	0
Quoted Prices in Active Markets (Level 1) | Other noncurrent assets | Cross-currency interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	0	0
Quoted Prices in Active Markets (Level 1) | Other noncurrent assets | Interest rate cap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	0
Quoted Prices in Active Markets (Level 1) | Other current liabilities | Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0	0
Quoted Prices in Active Markets (Level 1) | Other noncurrent liabilities | Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0	0
Quoted Prices in Active Markets (Level 1) | Other noncurrent liabilities | Equity swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability		0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets fair value	23	23
Financial liabilities fair value	15	15
Significant Other Observable Inputs (Level 2) | Other current assets | Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	8	8
Significant Other Observable Inputs (Level 2) | Other current assets | Cross-currency interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	12
Significant Other Observable Inputs (Level 2) | Other noncurrent assets | Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	1	2
Significant Other Observable Inputs (Level 2) | Other noncurrent assets | Cross-currency interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	1	13
Significant Other Observable Inputs (Level 2) | Other noncurrent assets | Interest rate cap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	1
Significant Other Observable Inputs (Level 2) | Other current liabilities | Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	12	11
Significant Other Observable Inputs (Level 2) | Other noncurrent liabilities | Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	3	2
Significant Other Observable Inputs (Level 2) | Other noncurrent liabilities | Equity swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability		2
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets fair value	0	0
Financial liabilities fair value	0	0
Significant Unobservable Inputs (Level 3) | Other current assets | Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	0	0
Significant Unobservable Inputs (Level 3) | Other current assets | Cross-currency interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	0
Significant Unobservable Inputs (Level 3) | Other noncurrent assets | Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	0	0
Significant Unobservable Inputs (Level 3) | Other noncurrent assets | Cross-currency interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	0	0
Significant Unobservable Inputs (Level 3) | Other noncurrent assets | Interest rate cap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	0
Significant Unobservable Inputs (Level 3) | Other current liabilities | Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0	0
Significant Unobservable Inputs (Level 3) | Other noncurrent liabilities | Foreign currency exchange derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	$ 0	0
Significant Unobservable Inputs (Level 3) | Other noncurrent liabilities | Equity swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability		$ 0