Accumulated other comprehensive income (loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Feb. 28, 2021	Feb. 29, 2020	Feb. 28, 2021	Feb. 29, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 20,563	$ 24,314	$ 21,136	$ 24,152
Total other comprehensive income	385	(94)	476	505
Ending balance	21,625	24,334	21,625	24,334
Pension/ post-retirement obligations
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(736)	(55)	(748)	(48)
Other comprehensive income (loss) before reclassification adjustments	(1)	4	16	(8)
Amounts reclassified from AOCI	(2)	(3)	(4)	(1)
Tax benefit (provision)	1	(2)	(3)	(1)
Total other comprehensive income	(2)	(1)	9	(9)
Ending balance	(739)	(57)	(739)	(57)
Unrealized gain (loss) on cash flow hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(27)	(24)	(31)	(24)
Other comprehensive income (loss) before reclassification adjustments	10	0	14	(1)
Amounts reclassified from AOCI	1	1	3	3
Tax benefit (provision)	(3)	0	(4)	(1)
Total other comprehensive income	9	1	13	1
Ending balance	(18)	(24)	(18)	(24)
Net investment hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(41)	14	(34)	55
Other comprehensive income (loss) before reclassification adjustments	(65)	27	(80)	(28)
Amounts reclassified from AOCI		0	0	0
Tax benefit (provision)	16	(7)	24	7
Total other comprehensive income	(49)	21	(56)	(21)
Ending balance	(90)	34	(90)	34
Share of OCI of equity method investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(5)	(5)	(10)	3
Other comprehensive income (loss) before reclassification adjustments	13	6	19	(5)
Amounts reclassified from AOCI	0	0	0	0
Tax benefit (provision)	2	(2)	1	0
Total other comprehensive income	15	4	20	(5)
Ending balance	10	(1)	10	(1)
Cumulative translation adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(2,873)	(3,242)	(2,948)	(3,884)
Other comprehensive income (loss) before reclassification adjustments	402	(121)	474	520
Amounts reclassified from AOCI	2	0	5	0
Tax benefit (provision)	0	3	0	3
Total other comprehensive income	404	(119)	479	524
Ending balance	(2,469)	(3,360)	(2,469)	(3,360)
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(3,682)	(3,313)	(3,771)	(3,897)
Other comprehensive income (loss) before reclassification adjustments	359	(84)	444	479
Amounts reclassified from AOCI	1	(2)	4	2
Tax benefit (provision)	16	(8)	17	9
Total other comprehensive income	376	(94)	465	490
Ending balance	$ (3,306)	$ (3,407)	$ (3,306)	$ (3,407)