Leases - changes in reserve for facility closings and related lease termination (Details) - USD ($) $ in Millions	12 Months Ended
	Aug. 31, 2018	Aug. 31, 2017
Changes in Reserve for Facility Closing and Related Lease Termination Charges [Roll Forward]
Balance at beginning of period	$ 718	$ 466
Provision for present value of non-cancelable lease payments on closed facilities	52	344
Changes in assumptions	19	13
Accretion expense	58	37
Other - non cash	338	0
Cash payments, net of sublease income	(221)	(142)
Balance at end of period	$ 964	$ 718