Leases - additional information (Details) $ in Millions	12 Months Ended
	Aug. 31, 2017 USD ($) lease	Aug. 31, 2016 USD ($)	Aug. 31, 2015 USD ($)
Operating Leased Assets [Line Items]
Interval period of renewal options	5 years
Proceeds from sale leaseback transactions	$ 444	$ 60	$ 867
Total minimum lease payments	32,811
Imputed interest and executory costs	900
Sublease rentals	270
Charges related to facilities that were closed or relocated	$ 394	$ 127	$ 252
Number of leases | lease	70
Minimum
Operating Leased Assets [Line Items]
Initial term of operating lease	15 years
Maximum
Operating Leased Assets [Line Items]
Initial term of operating lease	25 years
Potential undiscounted future payments	$ 327
Facility Closing
Operating Leased Assets [Line Items]
Total minimum lease payments	$ 1,370