Retirement Plans (Details 8) (USD $) In Millions, unless otherwise specified	May 31, 2013		May 31, 2012
Defined Benefit Plan Pension Plans With Accumulated Benefit Obligations In Excess Of Plan Assets [Abstract]
ABO	$ (21,930)	[1]	$ (21,555)	[1]
Fair value of plan assets	19,404		17,333
PBO	(22,570)		(22,185)
Net funded status	(3,166)		(4,852)
Defined Benefit Plan Plans With Benefit Obligations In Excess Of Plan Assets [Abstract]
Fair value of plan assets	19,433		17,334
PBO	(22,600)		(22,187)
Net funded status	$ (3,167)		$ (4,853)

[1] ABO not used in determination of funded status.