Accumulated other comprehensive income (loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Feb. 29, 2020	Feb. 28, 2019	Feb. 29, 2020	Feb. 28, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 24,314	$ 26,263	$ 24,152	$ 26,689
Total other comprehensive income (loss)	(94)	536	505	304
Ending Balance	24,334	25,413	24,334	25,413
Pension/ post-retirement obligations
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(55)	97	(48)	101
Other comprehensive income (loss) before reclassification adjustments	4	0	(8)	0
Amounts reclassified from AOCI	(3)	(4)	(1)	(8)
Other		0		0
Tax benefit (provision)	(2)	2	(1)	2
Total other comprehensive income (loss)	(1)	(2)	(9)	(6)
Ending Balance	(57)	95	(57)	95
Unrealized gain (loss) on cash flow hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(24)	(27)	(24)	(30)
Other comprehensive income (loss) before reclassification adjustments	0	(3)	(1)	0
Amounts reclassified from AOCI	1	2	3	3
Other		0		0
Tax benefit (provision)	0	0	(1)	(1)
Total other comprehensive income (loss)	1	(1)	1	2
Ending Balance	(24)	(28)	(24)	(28)
Net investment hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	14	0	55	0
Other comprehensive income (loss) before reclassification adjustments	27	(16)	(28)	(16)
Amounts reclassified from AOCI		0		0
Other		0		0
Tax benefit (provision)	(7)	4	7	4
Total other comprehensive income (loss)	21	(12)	(21)	(12)
Ending Balance	34	(12)	34	(12)
Share of OCI of equity method investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(5)	4	3	3
Other comprehensive income (loss) before reclassification adjustments	6	(2)	(5)	(1)
Amounts reclassified from AOCI	0	0	0	0
Other		0		0
Tax benefit (provision)	(2)	0	0	0
Total other comprehensive income (loss)	4	(2)	(5)	(1)
Ending Balance	(1)	2	(1)	2
Cumulative translation adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(3,242)	(3,305)	(3,884)	(3,076)
Other comprehensive income (loss) before reclassification adjustments	(121)	537	520	309
Amounts reclassified from AOCI	0	0	0	0
Other		7		7
Tax benefit (provision)	3	(1)	3	(2)
Total other comprehensive income (loss)	(119)	543	524	314
Ending Balance	(3,360)	(2,762)	(3,360)	(2,762)
Accumulated other comprehensive income (loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(3,313)	(3,231)	(3,897)	(3,002)
Other comprehensive income (loss) before reclassification adjustments	(84)	516	479	292
Amounts reclassified from AOCI	(2)	(2)	2	(5)
Other		7		7
Tax benefit (provision)	(8)	5	9	3
Total other comprehensive income (loss)	(94)	526	490	297
Ending Balance	$ (3,407)	$ (2,705)	$ (3,407)	$ (2,705)