Leases (Details) $ in Millions	3 Months Ended
	Nov. 30, 2015 USD ($) Lease	Aug. 31, 2015 USD ($)	Nov. 30, 2014 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	$ 54		$ 291
Charges related to facilities that were closed or relocated	66		$ 26
Changes in reserve for facility closings and related lease termination charges [Roll Forward]
Balance - beginning of period	446	$ 257
Provision for present value of non-cancellable lease payments on closed facilities	70	231
Assumptions about future sublease income, terminations and changes in interest rates	(9)	(6)
Interest accretion	5	27
Liability assumed through acquisition of Alliance Boots	0	13
Cash payments, net of sublease income	(26)	(76)
Balance - end of period	$ 486	$ 446
Number of leases | Lease	71
Maximum potential undiscounted future payments	$ 347