Accumulated other comprehensive income (loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Aug. 31, 2018	Aug. 31, 2017	Aug. 31, 2016
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	$ 28,274	$ 30,281	$ 31,300
Total other comprehensive income (loss)	50	(95)	(2,834)
Ending Balance	26,689	28,274	30,281
Pension/post-retirement obligations
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(139)	(212)	29
Other comprehensive income (loss) before reclassification adjustments	417	(34)	(303)
Amounts reclassified from accumulated OCI	(120)	109	0
Tax benefit (provision)	(57)	(2)	62
Total other comprehensive income (loss)	240	73	(241)
Ending Balance	101	(139)	(212)
Unrecognized gain (loss) on available-for-sale investments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	0	2	259
Other comprehensive income (loss) before reclassification adjustments	0	(2)	(148)
Amounts reclassified from accumulated OCI	0	0	(268)
Tax benefit (provision)	0	0	159
Total other comprehensive income (loss)	0	(2)	(257)
Ending Balance	0	0	2
Unrealized gain (loss) on cash flow hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(33)	(37)	(40)
Other comprehensive income (loss) before reclassification adjustments	0	0	0
Amounts reclassified from accumulated OCI	4	5	5
Tax benefit (provision)	(1)	(1)	(2)
Total other comprehensive income (loss)	3	4	3
Ending Balance	(30)	(33)	(37)
Share of OCI of equity method investments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(2)	(1)	0
Other comprehensive income (loss) before reclassification adjustments	(4)	(1)	(1)
Amounts reclassified from accumulated OCI	11	0	0
Tax benefit (provision)	(2)	0	0
Total other comprehensive income (loss)	5	(1)	(1)
Ending Balance	3	(2)	(1)
Cumulative translation adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(2,877)	(2,744)	(462)
Other comprehensive income (loss) before reclassification adjustments	(207)	(133)	(2,279)
Amounts reclassified from accumulated OCI	8	0	(3)
Tax benefit (provision)	0	0	0
Total other comprehensive income (loss)	(199)	(133)	(2,282)
Ending Balance	(3,076)	(2,877)	(2,744)
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(3,051)	(2,992)	(214)
Other comprehensive income (loss) before reclassification adjustments	206	(170)	(2,731)
Amounts reclassified from accumulated OCI	(97)	114	(266)
Tax benefit (provision)	(60)	(3)	219
Total other comprehensive income (loss)	49	(59)	(2,778)
Ending Balance	$ (3,002)	$ (3,051)	$ (2,992)