Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2013
Accumulated Other Comprehensive Income [Line Items]
Beginning balance	$ 506	$ 607
Ending balance	172	506	$ 607
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	17,110	16,171	16,055
PROVISION FOR INCOME TAXES	577	1,334	1,622
Amortization of prior service credits [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	115	115	114
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income [Line Items]
Beginning balance	81	106	65
Translation adjustment	(334)	(25)	41
Ending balance	(253)	81	106
Retirement Plans Adjustments [Member]
Accumulated Other Comprehensive Income [Line Items]
Beginning balance	425	501	564
Net gain (loss) and other arising during period	72	1	0
Reclassification from AOCI	(72)	(77)	(63)
Ending balance	425	425	501
Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	115	115	114
PROVISION FOR INCOME TAXES	(43)	(38)	(51)
Net Income	$ 72	$ 77	$ 63