Accumulated other comprehensive income (loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Feb. 28, 2019	Feb. 28, 2018	Feb. 28, 2019	Feb. 28, 2018
AOCI [Roll Forward]
Beginning Balance	$ 26,263	$ 26,756	$ 26,689	$ 28,274
Total other comprehensive income (loss)	536	386	304	908
Ending Balance	25,413	28,178	25,413	28,178
Pension/ post- retirement obligations
AOCI [Roll Forward]
Beginning Balance	97	(139)	101	(139)
Other comprehensive income (loss) before reclassification adjustments	0	0	0	(1)
Amounts reclassified from AOCI	(4)	(3)	(8)	(3)
Other	0		0
Tax benefit (provision)	2	1	2	2
Total other comprehensive income (loss)	(2)	(2)	(6)	(2)
Ending Balance	95	(141)	95	(141)
Unrealized gain (loss) on hedges
AOCI [Roll Forward]
Beginning Balance	(27)	(33)	(30)	(33)
Other comprehensive income (loss) before reclassification adjustments	(19)	0	(16)	0
Amounts reclassified from AOCI	2	1	3	2
Other	0		0
Tax benefit (provision)	4	0	3	(1)
Total other comprehensive income (loss)	(13)	1	(10)	1
Ending Balance	(40)	(32)	(40)	(32)
Share of AOCI of equity method investments
AOCI [Roll Forward]
Beginning Balance	4	0	3	(2)
Other comprehensive income (loss) before reclassification adjustments	(2)	1	(1)	4
Amounts reclassified from AOCI	0	0	0	0
Other	0		0
Tax benefit (provision)	0	(1)	0	(2)
Total other comprehensive income (loss)	(2)	0	(1)	2
Ending Balance	2	0	2	0
Cumulative translation adjustments
AOCI [Roll Forward]
Beginning Balance	(3,305)	(2,371)	(3,076)	(2,877)
Other comprehensive income (loss) before reclassification adjustments	537	381	309	887
Amounts reclassified from AOCI	0	0	0	0
Other	7		7
Tax benefit (provision)	(1)	0	(2)	0
Total other comprehensive income (loss)	543	381	314	887
Ending Balance	(2,762)	(1,990)	(2,762)	(1,990)
Accumulated other comprehensive income (loss)
AOCI [Roll Forward]
Beginning Balance	(3,231)	(2,543)	(3,002)	(3,051)
Other comprehensive income (loss) before reclassification adjustments	516	382	292	890
Amounts reclassified from AOCI	(2)	(2)	(5)	(1)
Other	7		7
Tax benefit (provision)	5	0	3	(1)
Total other comprehensive income (loss)	526	380	297	888
Ending Balance	$ (2,705)	$ (2,163)	$ (2,705)	$ (2,163)