Leases (Details) $ in Millions	12 Months Ended
	Aug. 31, 2015 USD ($) Lease	Aug. 31, 2014 USD ($)	Aug. 31, 2013 USD ($)
Leases [Abstract]
Initial term of operating lease, lower range	15 years
Initial term of operating lease, upper range	25 years
Proceeds from sale leaseback transactions	$ 867	$ 67	$ 115
Charges related to facilities that were closed or relocated	252	177	43
Financing Obligation [Abstract]
2016	18
2017	18
2018	18
2019	18
2020	18
Later	1,234
Total minimum lease payments	1,324
Capital Lease [Abstract]
2016	69
2017	65
2018	62
2019	60
2020	61
Later	881
Total minimum lease payments	1,198
Operating Lease [Abstract]
2016	3,141
2017	3,008
2018	2,944
2019	2,734
2020	2,518
Later	23,625
Total minimum lease payments	37,970
Executory costs and imputed interest	1,600
Minimum sublease rentals	214
Changes in reserve for facility closings and related lease termination charges [Roll Forward]
Balance - beginning of period	257	123
Provision for present value of non-cancellable lease payments on closed facilities	231	171
Assumptions about future sublease income, terminations and changes in interest rates	(6)	(8)
Interest accretion	27	14
Liability assumed through acquisition of Alliance Boots	13	0
Cash payments, net of sublease income	(76)	(43)
Balance - end of period	$ 446	257	123
Number of assigned leases (in number of lease) | Lease	71
Maximum potential undiscounted future payments	$ 351
Rent Expense [Abstract]
Minimum rentals	3,176	2,687	2,644
Contingent rentals	38	5	6
Less: Sublease rental income	(46)	(22)	(22)
Total rental expense	$ 3,168	$ 2,670	$ 2,628