Derivative Instruments and Hedging Activities - Derivatives Gains and Losses (Details) - USD ($)	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain (loss) on derivatives	$ 3,000,000	$ (12,000,000)	$ (13,000,000)	$ (18,000,000)
Foreign currency exchange derivatives | Cost of sales
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain (loss) on foreign currency exchange derivatives not designated as hedging instrument	(1,000,000)	1,000,000	(1,000,000)	(1,000,000)
Foreign currency exchange derivatives | Selling, general and administrative
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain (loss) on equity swap derivatives not designated as hedging instrument	4,000,000	(12,000,000)	(13,000,000)	(15,000,000)
Foreign currency exchange derivatives | Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gains (losses)	3,000,000	15,000,000	(1,000,000)	8,000,000
Ineffective portion of gain (loss) recognized in income	0	0	0	0
Foreign currency exchange derivatives | Cash Flow Hedging | Cost of sales
Derivative Instruments, Gain (Loss) [Line Items]
Effective portion of pretax gain (loss) reclassified from AOCI into income	(2,000,000)	1,000,000	(2,000,000)	2,000,000
Foreign currency exchange derivatives | Net Investment Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Effective portion of pretax gains (loss) related to net investment hedges	22,000,000	(37,000,000)	44,000,000	(54,000,000)
Gains (losses) reclassified into income for net investment hedges	0	0	0	0
Equity swaps | Net financing charges
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain (loss) on foreign currency exchange derivatives not designated as hedging instrument	$ 0	$ (1,000,000)	$ 1,000,000	$ (2,000,000)