Accumulated Other Comprehensive Income (Loss) - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Aug. 31, 2017	Aug. 31, 2016
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	$ 16,073
Translation adjustments	109	$ 12
Ending balance	16,618
Foreign Currency Translation Loss [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(685)	(514)
Translation adjustments	109	12
Ending balance	(576)	(502)
Retirement Plans Adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	270	345
Reclassifications from AOCI	(19)	(19)
Ending balance	251	326
Accumulated Other Comprehensive (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Ending balance	$ (325)	$ (176)