Financial Instruments - Reconciliation of Changes in Fair Value (Details) - Level 3 - Foreign currency option contracts - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair Value, beginning of period	$ 3	$ 2
Purchases, issuances, sales and settlements:
Purchases	0	0
Settlements	0	0
Transfer in and / or out of Level 3	0	0
Reclass between short-term and long-term	0	0
Fair Value, end of period	3	3
Short-term
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair Value, beginning of period	2	0
Purchases, issuances, sales and settlements:
Purchases	0	0
Settlements	0	0
Transfer in and / or out of Level 3	0	0
Reclass between short-term and long-term	0	1
Fair Value, end of period	2	1
Long-term
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair Value, beginning of period	1	2
Purchases, issuances, sales and settlements:
Purchases	0	0
Settlements	0	0
Transfer in and / or out of Level 3	0	0
Reclass between short-term and long-term	0	(1)
Fair Value, end of period	1	2
Included in other income
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Total unrealized gains (losses)	0	0
Total realized gains (losses)	0	0
Included in other income | Short-term
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Total unrealized gains (losses)	0	0
Total realized gains (losses)	0	0
Included in other income | Long-term
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Total unrealized gains (losses)	0	0
Total realized gains (losses)	0	0
Included in cost of sales
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Total unrealized gains (losses)	0	1
Total realized gains (losses)	0	0
Included in cost of sales | Short-term
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Total unrealized gains (losses)	0	0
Total realized gains (losses)	0	0
Included in cost of sales | Long-term
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Total unrealized gains (losses)	0	1
Total realized gains (losses)	$ 0	$ 0