Accumulated other comprehensive income (loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Feb. 28, 2018	Feb. 28, 2017	Feb. 28, 2018	Feb. 28, 2017
AOCI [Roll Forward]
Beginning Balance			$ 28,274	$ 30,281
Net other comprehensive income (loss)	$ 386	$ 5	908	(860)
Ending Balance	28,178	30,421	28,178	30,421
Pension/ post- retirement obligations
AOCI [Roll Forward]
Beginning Balance	(139)	(221)	(139)	(212)
Other comprehensive income (loss) before reclassification adjustments	0	6	(1)	(5)
Amounts reclassified from accumulated OCI	(3)	0	(3)	0
Tax benefit (provision)	1	(1)	2	1
Net other comprehensive income (loss)	(2)	5	(2)	(4)
Ending Balance	(141)	(216)	(141)	(216)
Unrecognized gain (loss) on available-for- sale investments
AOCI [Roll Forward]
Beginning Balance	0	1	0	2
Other comprehensive income (loss) before reclassification adjustments	0	0	0	(1)
Amounts reclassified from accumulated OCI	0	0	0	0
Tax benefit (provision)	0	0	0	0
Net other comprehensive income (loss)	0	0	0	(1)
Ending Balance	0	1	0	1
Unrealized gain (loss) on cash flow hedges
AOCI [Roll Forward]
Beginning Balance	(33)	(36)	(33)	(37)
Other comprehensive income (loss) before reclassification adjustments	0	0	0	0
Amounts reclassified from accumulated OCI	1	1	2	3
Tax benefit (provision)	0	0	(1)	(1)
Net other comprehensive income (loss)	1	1	1	2
Ending Balance	(32)	(35)	(32)	(35)
Share of OCI of equity method investments
AOCI [Roll Forward]
Beginning Balance	0	(2)	(2)	(1)
Other comprehensive income (loss) before reclassification adjustments	1	(7)	4	(8)
Amounts reclassified from accumulated OCI	0	0	0	0
Tax benefit (provision)	(1)	3	(2)	3
Net other comprehensive income (loss)	0	(4)	2	(5)
Ending Balance	0	(6)	0	(6)
Currency translation adjustment
AOCI [Roll Forward]
Beginning Balance	(2,371)	(3,552)	(2,877)	(2,744)
Other comprehensive income (loss) before reclassification adjustments	381	(1)	887	(809)
Amounts reclassified from accumulated OCI	0	0	0	0
Tax benefit (provision)	0	0	0	0
Net other comprehensive income (loss)	381	(1)	887	(809)
Ending Balance	(1,990)	(3,553)	(1,990)	(3,553)
Accumulated other comprehensive (loss) income
AOCI [Roll Forward]
Beginning Balance	(2,543)	(3,810)	(3,051)	(2,992)
Other comprehensive income (loss) before reclassification adjustments	382	(2)	890	(823)
Amounts reclassified from accumulated OCI	(2)	1	(1)	3
Tax benefit (provision)	0	2	(1)	3
Net other comprehensive income (loss)	380	1	888	(817)
Ending Balance	$ (2,163)	$ (3,809)	$ (2,163)	$ (3,809)