Accumulated other comprehensive income (loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Aug. 31, 2020	Aug. 31, 2019	Aug. 31, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	$ 24,152	$ 26,689	$ 28,274
Total other comprehensive income (loss)	148	(909)	50
Ending Balance	21,136	24,152	26,689
Accumulated other comprehensive income (loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(3,897)	(3,002)	(3,051)
Other comprehensive income (loss) before reclassification adjustments	(69)	(889)	206
Amounts reclassified from AOCI	0	(12)	(97)
Tax benefit (provision)	195	5	(60)
Total other comprehensive income (loss)	126	(896)	49
Ending Balance	(3,771)	(3,897)	(3,002)
Pension/post-retirement obligations
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(48)	101	(139)
Other comprehensive income (loss) before reclassification adjustments	(861)	(162)	417
Amounts reclassified from AOCI	(8)	(17)	(120)
Tax benefit (provision)	169	30	(57)
Total other comprehensive income (loss)	(700)	(149)	240
Ending Balance	(748)	(48)	101
Unrealized gain (loss) on cash flow hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(24)	(30)	(33)
Other comprehensive income (loss) before reclassification adjustments	(12)	1	0
Amounts reclassified from AOCI	5	5	4
Tax benefit (provision)	1	(1)	(1)
Total other comprehensive income (loss)	(6)	5	3
Ending Balance	(31)	(24)	(30)
Net investment hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	55	0	0
Other comprehensive income (loss) before reclassification adjustments	(113)	73	0
Amounts reclassified from AOCI	0	0	0
Tax benefit (provision)	23	(18)	0
Total other comprehensive income (loss)	(90)	55	0
Ending Balance	(34)	55	0
Share of OCI of equity method investments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	3	3	(2)
Other comprehensive income (loss) before reclassification adjustments	(16)	(1)	(4)
Amounts reclassified from AOCI	0	0	11
Tax benefit (provision)	3	0	(2)
Total other comprehensive income (loss)	(13)	(1)	5
Ending Balance	(10)	3	3
Cumulative translation adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(3,884)	(3,076)	(2,877)
Other comprehensive income (loss) before reclassification adjustments	934	(801)	(207)
Amounts reclassified from AOCI	3	0	8
Tax benefit (provision)	(1)	(6)	0
Total other comprehensive income (loss)	936	(807)	(199)
Ending Balance	$ (2,948)	$ (3,884)	$ (3,076)