Leases and Store Closures (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Feb. 28, 2015 Lease	Feb. 28, 2014	Feb. 28, 2015 Lease	Feb. 28, 2014	Aug. 31, 2014
Leases and Store Closures [Abstract]
Initial term of operating lease, lower range			15 years
Initial term of operating lease, upper range			25 years
Financing Obligation [Abstract]
2015	$ 19		$ 19
2016	18		18
2017	18		18
2018	18		18
2019	18		18
Later	1,153		1,153
Total minimum lease payments	1,244		1,244
Capital Lease [Abstract]
2015	68		68
2016	66		66
2017	62		62
2018	59		59
2019	59		59
Later	901		901
Total minimum lease payments	1,215		1,215
Operating Lease [Abstract]
2015	3,071		3,071
2016	3,006		3,006
2017	2,886		2,886
2018	2,814		2,814
2019	2,561		2,561
Later	23,102		23,102
Total minimum lease payments	37,440		37,440
Executory costs and imputed interest	1,600		1,600
Minimum sublease rentals	211		211
Pre-tax charges	0	0	17	0
Charges related to facilities that were closed or relocated	0	6	26	33
Changes in reserve for facility closings and related lease termination charges [Roll Forward]
Balance - beginning of period			257	123	123
Provision for present value of non-cancellable lease payments on closed facilities			11		171
Assumptions about future sublease income, terminations and changes in interest rates			2		(8)
Interest accretion			13		14
Liability assumed through acquisition of Alliance Boots			13		0
Cash payments, net of sublease income			(36)		(43)
Balance - end of period	260		260		257
Number of leases	72		72
Maximum potential undiscounted future payments	360		360
Rent Expense [Abstract]
Minimum rentals	809	673	1,486	1,333
Contingent rentals	1	1	3	4
Less: Sublease rental income	(6)	(7)	(11)	(12)
Total rental expense	$ 804	$ 667	$ 1,478	$ 1,325