Derivative Instruments and Hedging Activities - Derivatives Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gain (loss) on derivatives	$ (1)	$ (16)
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)	0
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	0	(17)
Foreign currency exchange derivatives | Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gains (losses)	22	(4)
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	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