Operating Leases (Details) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	May 31, 2016 USD ($) Lease	May 31, 2015 USD ($)	May 31, 2016 USD ($) Lease	May 31, 2015 USD ($)	Aug. 31, 2015 USD ($)
Operating Leased Assets [Line Items]
Interval period of renewal options			5 years
Charges related to facilities that were closed or relocated	$ 16	$ 34	$ 91	$ 60
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			89		231
Assumptions about future sublease income, terminations and changes in interest rates			(19)		(6)
Interest accretion			21		27
Liability assumed through acquisition of Alliance Boots			0		13
Cash payments, net of sublease income			(81)		(76)
Balance - end of period	$ 456		$ 456		$ 446
Number of leases | Lease	76		76
Maximum potential undiscounted future payments	$ 343		$ 343
Minimum [Member]
Operating Leased Assets [Line Items]
Initial term of operating lease			15 years
Maximum [Member]
Operating Leased Assets [Line Items]
Initial term of operating lease			25 years