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Financial instruments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
Financial instruments (Details) - USD ($) $ in Millions	Feb. 28, 2021	Feb. 29, 2020	Feb. 28, 2021	Feb. 29, 2020	Aug. 31, 2020
Foreign currency forwards \| Not Designated as Hedging Instrument \| Selling, general and administrative expenses
Derivatives, Fair Value [Line Items]
Gains and (losses) due to changes in fair value of derivative instruments	$ (95)	$ 13	$ (124)	$ (61)
Foreign currency forwards \| Not Designated as Hedging Instrument \| Other income (expense)
Derivatives, Fair Value [Line Items]
Gains and (losses) due to changes in fair value of derivative instruments	7	(7)	(1)	4
Total return swap \| Not Designated as Hedging Instrument \| Selling, general and administrative expenses
Derivatives, Fair Value [Line Items]
Gains and (losses) due to changes in fair value of derivative instruments	16	$ 0	29	$ 0
Other non-current assets \| Interest rate swaps \| Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount, assets	1,000		1,000
Fair value, assets	7		7
Other non-current assets \| Cross currency interest rate swaps \| Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount, assets					$ 722
Fair value, assets					16
Other current assets \| Foreign currency forwards \| Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount, assets					100
Fair value, assets					1
Other current assets \| Foreign currency forwards \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount, assets	741		741		1,930
Fair value, assets	11		11		19
Other current assets \| Cross currency interest rate swaps \| Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount, assets					50
Fair value, assets					0
Other non-current liabilities \| Interest rate swaps \| Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount, liabilities					1,000
Fair value, liabilities					10
Other non-current liabilities \| Foreign currency forwards \| Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount, liabilities	40		40		49
Fair value, liabilities	2		2		1
Other non-current liabilities \| Cross currency interest rate swaps \| Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount, liabilities	977		977		318
Fair value, liabilities	42		42		13
Other current liabilities \| Foreign currency forwards \| Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount, liabilities	551		551		671
Fair value, liabilities	14		14		23
Other current liabilities \| Foreign currency forwards \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount, liabilities	2,870		2,870		2,934
Fair value, liabilities	41		41		56
Other current liabilities \| Cross currency interest rate swaps \| Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount, liabilities	163		163		103
Fair value, liabilities	13		13		3
Other current liabilities \| Total return swap \| Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount, liabilities	237		237		205
Fair value, liabilities	$ 4		$ 4		$ 1