Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Aug. 31, 2015	Aug. 31, 2014
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	$ 172
Translation adjustment	(138)	$ (31)
Amortization of prior service credit, net of tax of $7 in 2015 and $10 in 2014	(24)	(16)
Ending balance	10	459
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	4,525	4,114
PROVISION FOR INCOME TAXES	392	359
Foreign currency translation gain (loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(253)	81
Translation adjustment	(138)	(31)
Ending balance	(391)	50
Retirement plans adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	425	425
Reclassification from AOCI	(24)	(16)
Ending balance	401	409
Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	31	26
PROVISION FOR INCOME TAXES	(7)	(10)
Net income	$ 24	$ 16