Leases (Details) $ in Millions	12 Months Ended
	Aug. 31, 2016 USD ($) Lease	Aug. 31, 2015 USD ($)	Aug. 31, 2014 USD ($)
Leases [Abstract]
Interval period of renewal options	5 years
Proceeds from sale leaseback transactions	$ 60	$ 867	$ 67
Financing Obligation [Abstract]
2017	18
2018	18
2019	18
2020	18
2021	18
Later	1,267
Total minimum lease payments	1,357
Capital Lease [Abstract]
2017	68
2018	62
2019	59
2020	58
2021	57
Later	966
Total minimum lease payments	1,270
Operating Lease [Abstract]
2017	3,066
2018	2,972
2019	2,826
2020	2,632
2021	2,403
Later	20,190
Total minimum lease payments	34,089
Imputed interest and executory costs	1,700
Charges related to facilities that were closed or relocated	$ 127	252	177
Number of leases | Lease	79
Changes in reserve for facility closings and related lease termination charges [Roll Forward]
Balance at beginning of period	$ 446	257
Provision for present value of non-cancellable lease payments on closed facilities	134	231
Assumptions about future sublease income, terminations and changes in interest rates	(34)	(6)
Interest accretion	27	27
Liability assumed through acquisition of Alliance Boots	0	13
Cash payments, net of sublease income	(107)	(76)
Balance at end of period	466	446	257
Rent Expense [Abstract]
Minimum rentals	3,355	3,176	2,687
Contingent rentals	60	38	5
Less: Sublease rental income	(49)	(46)	(22)
Total rental expense	$ 3,366	$ 3,168	$ 2,670
Minimum [Member]
Leases [Abstract]
Initial term of operating lease	15 years
Operating Lease [Abstract]
Sublease rentals	$ 199
Maximum [Member]
Leases [Abstract]
Initial term of operating lease	25 years
Operating Lease [Abstract]
Potential undiscounted future payments	$ 340