Financial instruments - derivative instruments (Details) - USD ($) $ in Millions	Aug. 31, 2021	Aug. 31, 2020
Cross currency interest rate swaps | Derivatives designated as hedges: | Other non-current assets
Derivatives, Fair Value [Line Items]
Notional amount, assets	$ 155	$ 722
Fair value, assets	1	16
Cross currency interest rate swaps | Derivatives designated as hedges: | Other current assets
Derivatives, Fair Value [Line Items]
Notional amount, assets		50
Fair value, assets		0
Cross currency interest rate swaps | Derivatives designated as hedges: | Other non-current liabilities
Derivatives, Fair Value [Line Items]
Notional amount, liabilities	801	318
Fair value, liabilities	23	13
Cross currency interest rate swaps | Derivatives designated as hedges: | Other current liabilities
Derivatives, Fair Value [Line Items]
Notional amount, liabilities	109	103
Fair value, liabilities	9	3
Foreign currency forwards | Derivatives designated as hedges: | Other non-current assets
Derivatives, Fair Value [Line Items]
Notional amount, assets	6
Fair value, assets	0
Foreign currency forwards | Derivatives designated as hedges: | Other current assets
Derivatives, Fair Value [Line Items]
Notional amount, assets	575	100
Fair value, assets	7	1
Foreign currency forwards | Derivatives designated as hedges: | Other non-current liabilities
Derivatives, Fair Value [Line Items]
Notional amount, liabilities	23	49
Fair value, liabilities	1	1
Foreign currency forwards | Derivatives designated as hedges: | Other current liabilities
Derivatives, Fair Value [Line Items]
Notional amount, liabilities	31	671
Fair value, liabilities	1	23
Foreign currency forwards | Derivatives not designated as hedges: | Other current assets
Derivatives, Fair Value [Line Items]
Notional amount, assets	3,636	1,930
Fair value, assets	38	19
Foreign currency forwards | Derivatives not designated as hedges: | Other current liabilities
Derivatives, Fair Value [Line Items]
Notional amount, liabilities	808	2,934
Fair value, liabilities	3	56
Interest rate swaps | Derivatives designated as hedges: | Other non-current liabilities
Derivatives, Fair Value [Line Items]
Notional amount, liabilities		1,000
Fair value, liabilities		10
Total return swap | Derivatives not designated as hedges: | Other current assets
Derivatives, Fair Value [Line Items]
Notional amount, assets	224
Fair value, assets	2
Total return swap | Derivatives not designated as hedges: | Other current liabilities
Derivatives, Fair Value [Line Items]
Notional amount, liabilities	37	205
Fair value, liabilities	$ 0	$ 1