Operating leases (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	May 31, 2019	May 31, 2018	May 31, 2019	May 31, 2018	Aug. 31, 2018
Leases [Abstract]
Charges related to facilities that were closed or relocated	$ 53	$ 21	$ 95	$ 88
Changes in reserve for facility closings and related lease termination charges [Roll Forward]
Balance at beginning of period			964	$ 718	$ 718
Provision for present value of non-cancellable lease payments on closed facilities			11		52
Changes in assumptions			54		19
Accretion expense			30		58
Other - non cash			124		338
Cash payments, net of sublease income			(240)		(221)
Balance at end of period	$ 943		$ 943		$ 964