Operating leases (Details) $ in Millions	3 Months Ended		12 Months Ended
	Nov. 30, 2017 USD ($) lease	Nov. 30, 2016 USD ($)	Aug. 31, 2017 USD ($)
Operating Leased Assets [Line Items]
Interval period of renewal options	5 years
Proceeds from sale leaseback transactions	$ 0	$ 436
Charges related to facilities that were closed or relocated	$ 39	17
Number of leases | lease	71
Potential undiscounted future payments	$ 318
Changes in reserve for facility closings and related lease termination charges [Roll Forward]
Balance at beginning of period	718	$ 466	$ 466
Provision for present value of non-cancellable lease payments on closed facilities	29		344
Assumptions about future sublease income, terminations and changes in interest rates	1		13
Interest accretion	9		37
Cash payments, net of sublease income	(61)		(142)
Balance at end of period	$ 696		$ 718
Minimum
Operating Leased Assets [Line Items]
Initial term of operating lease	15 years
Maximum
Operating Leased Assets [Line Items]
Initial term of operating lease	25 years