Accumulated Other Comprehensive Income - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	$ 13,784	$ 14,993	$ 15,277
Translation adjustments	(171)	(261)	(334)
Ending balance	16,073	13,784	14,993
Foreign Currency Translation Gain (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(514)	(253)	81
Translation adjustments	(171)	(261)	(334)
Ending balance	(685)	(514)	(253)
Retirement Plans Adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	345	425	425
Prior service credit and other arising during period	1	(4)	72
Reclassifications from AOCI	(76)	(76)	(72)
Ending balance	270	345	425
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(169)	172	506
Ending balance	$ (415)	$ (169)	$ 172