Operating Leases (Details) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Feb. 29, 2016 USD ($) Lease	Feb. 28, 2015 USD ($)	Feb. 29, 2016 USD ($) Lease	Feb. 28, 2015 USD ($)	Aug. 31, 2015 USD ($)
Operating Leases [Abstract]
Initial term of operating lease, lower range			15 years
Initial term of operating lease, upper range			25 years
Interval period of renewal options			5 years
Charges related to facilities that were closed or relocated	$ 9	$ 0	$ 75	$ 26
Changes in reserve for facility closings and related lease termination charges [Roll Forward]
Balance - beginning of period			446	$ 257	$ 257
Provision for present value of non-cancellable lease payments on closed facilities			77		231
Assumptions about future sublease income, terminations and changes in interest rates			(14)		(6)
Interest accretion			12		27
Liability assumed through acquisition of Alliance Boots			0		13
Cash payments, net of sublease income			(54)		(76)
Balance - end of period	$ 467		$ 467		$ 446
Number of leases | Lease	79		79
Maximum potential undiscounted future payments	$ 348		$ 348