Leases - changes in reserve for facility closings and related lease termination (Details) - USD ($) $ in Millions	12 Months Ended
	Aug. 31, 2019	Aug. 31, 2018
Changes in Reserve for Facility Closing and Related Lease Termination Charges [Roll Forward]
Balance at beginning of period	$ 964	$ 718
Provision for present value of non-cancelable lease payments on closed facilities	90	52
Changes in assumptions	56	19
Accretion expense	39	58
Other - non cash	160	338
Cash payments, net of sublease income	(316)	(221)
Balance at end of period	$ 993	$ 964