Accumulated other comprehensive income (loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Aug. 31, 2019	Aug. 31, 2018	Aug. 31, 2017
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	$ 26,689	$ 28,274	$ 30,281
Total other comprehensive income (loss)	(909)	50	(95)
Ending Balance	24,152	26,689	28,274
Accumulated other comprehensive income (loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(3,002)	(3,051)	(2,992)
Other comprehensive income (loss) before reclassification adjustments	(889)	206	(170)
Amounts reclassified from AOCI	(12)	(97)	114
Tax benefit (provision)	5	(60)	(3)
Total other comprehensive income (loss)	(896)	49	(59)
Ending Balance	(3,897)	(3,002)	(3,051)
Pension/post-retirement obligations
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	101	(139)	(212)
Other comprehensive income (loss) before reclassification adjustments	(162)	417	(34)
Amounts reclassified from AOCI	(17)	(120)	109
Tax benefit (provision)	30	(57)	(2)
Total other comprehensive income (loss)	(149)	240	73
Ending Balance	(48)	101	(139)
Unrecognized gain (loss) on available-for- sale investments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	0	0	2
Other comprehensive income (loss) before reclassification adjustments	0	0	(2)
Amounts reclassified from AOCI	0	0	0
Tax benefit (provision)	0	0	0
Total other comprehensive income (loss)	0	0	(2)
Ending Balance	0	0	0
Unrealized gain (loss) on cash flow hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(30)	(33)	(37)
Other comprehensive income (loss) before reclassification adjustments	74	0	0
Amounts reclassified from AOCI	5	4	5
Tax benefit (provision)	(19)	(1)	(1)
Total other comprehensive income (loss)	60	3	4
Ending Balance	31	(30)	(33)
Share of OCI of equity method investments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	3	(2)	(1)
Other comprehensive income (loss) before reclassification adjustments	(1)	(4)	(1)
Amounts reclassified from AOCI	0	11	0
Tax benefit (provision)	0	(2)	0
Total other comprehensive income (loss)	(1)	5	(1)
Ending Balance	3	3	(2)
Cumulative translation adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(3,076)	(2,877)	(2,744)
Other comprehensive income (loss) before reclassification adjustments	(801)	(207)	(133)
Amounts reclassified from AOCI	0	8	0
Tax benefit (provision)	(6)	0	0
Total other comprehensive income (loss)	(807)	(199)	(133)
Ending Balance	$ (3,884)	$ (3,076)	$ (2,877)