Accumulated other comprehensive income (loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2017	May 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ 30,281
Net other comprehensive income (loss)	$ 511	$ 600	(349)	$ (1,090)
Ending Balance	31,484		31,484
Pension/post-retirement obligations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(216)	30	(212)	29
Other comprehensive income (loss) before reclassification adjustments	(102)	5	(107)	4
Amounts reclassified from accumulated OCI 1	109	0	109	0
Tax benefit (provision)	(2)	(2)	(1)	0
Net other comprehensive income (loss)	5	3	1	4
Ending Balance	(211)	33	(211)	33
Unrecognized gain (loss) on available-for-sale investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	1	172	2	259
Other comprehensive income (loss) before reclassification adjustments	(1)	(6)	(2)	(150)
Amounts reclassified from accumulated OCI 1	0	(268)	0	(268)
Tax benefit (provision)	0	102	0	159
Net other comprehensive income (loss)	(1)	(172)	(2)	(259)
Ending Balance	0	0	0	0
Unrealized gain (loss) on cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(35)	(38)	(37)	(40)
Other comprehensive income (loss) before reclassification adjustments	0	0	0	0
Amounts reclassified from accumulated OCI 1	1	1	4	4
Tax benefit (provision)	0	(1)	(1)	(2)
Net other comprehensive income (loss)	1	0	3	2
Ending Balance	(34)	(38)	(34)	(38)
Share of OCI of equity method investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(6)	0	(1)	0
Other comprehensive income (loss) before reclassification adjustments	4	0	(4)	0
Amounts reclassified from accumulated OCI 1	0	0	0	0
Tax benefit (provision)	(2)	0	1	0
Net other comprehensive income (loss)	2	0	(3)	0
Ending Balance	(4)	0	(4)	0
Currency translation adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(3,553)	(2,032)	(2,744)	(462)
Other comprehensive income (loss) before reclassification adjustments	499	762	(310)	(808)
Amounts reclassified from accumulated OCI 1	0	(2)	0	(2)
Tax benefit (provision)	0	0	0	0
Net other comprehensive income (loss)	499	760	(310)	(810)
Ending Balance	(3,054)	(1,272)	(3,054)	(1,272)
Total
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(3,809)	(1,868)	(2,992)	(214)
Other comprehensive income (loss) before reclassification adjustments	400	761	(423)	(954)
Amounts reclassified from accumulated OCI 1	110	(269)	113	(266)
Tax benefit (provision)	(4)	99	(1)	157
Net other comprehensive income (loss)	506	591	(311)	(1,063)
Ending Balance	$ (3,303)	$ (1,277)	$ (3,303)	$ (1,277)