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Financial instruments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Financial instruments (Details) - USD ($) $ in Millions	May 31, 2019	May 31, 2018	May 31, 2019	May 31, 2018	Aug. 31, 2018
Foreign currency forwards \| Not designated as hedges \| Selling, general and administrative expenses
Effect of Fair Value Hedges on Results of Operations [Abstract]
Gains and (losses) due to changes in fair value of derivative instruments	$ 140	$ 108	$ 80	$ (75)
Foreign currency forwards \| Not designated as hedges \| Other income (expense)
Effect of Fair Value Hedges on Results of Operations [Abstract]
Gains and (losses) due to changes in fair value of derivative instruments	(8)	$ 3	(10)	$ 36
Other current assets \| Foreign currency forwards \| Designated as hedges
Derivatives, Fair Value [Line Items]
Notional	37		37		$ 15
Fair value	1		1		0
Other current assets \| Foreign currency forwards \| Not designated as hedges
Derivatives, Fair Value [Line Items]
Notional	3,105		3,105		3,273
Fair value	107		107		52
Other non-current assets \| Cross currency interest rate swaps \| Designated as hedges
Derivatives, Fair Value [Line Items]
Notional	800		800
Fair value	39		39
Accrued expenses and other liabilities \| Interest rate swaps \| Designated as hedges
Derivatives, Fair Value [Line Items]
Notional					250
Fair value					1
Accrued expenses and other liabilities \| Foreign currency forwards \| Not designated as hedges
Derivatives, Fair Value [Line Items]
Notional	658		658		825
Fair value	$ 3		$ 3		$ 4