Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2016	May 31, 2015	May 31, 2014
Accumulated Other Comprehensive Income Net Of Tax [Abstract]
Foreign currency translation gain (loss): Beginning balance	$ (253)	$ 81	$ 106
Translation adjustment	(261)	(334)	(25)
Foreign currency translation gain (loss): Ending balance	(514)	(253)	81
Retirement plans adjustments: Beginning Balance	425	425	501
Prior service credit and other arising during period	(4)	72	1
Reclassification from AOCI	(76)	(72)	(77)
Retirement plans adjustments: Ending Balance	345	425	425
Accumulated other comprehensive (loss) income at end of period	(169)	172	506
Amortization of retirement plans prior service credits, before tax	(121)	(115)	(115)
Income tax benefit	45	43	38
AOCI reclassifications, net of tax	$ (76)	$ (72)	$ (77)