Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	May 31, 2013	May 31, 2012	May 31, 2011
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (4,953)	$ (2,550)	$ (2,440)
Other comprehensive gain (loss)	1,133	(2,403)	(110)
Ending balance	(3,820)	(4,953)	(2,550)
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	61	156	31
Other comprehensive gain (loss)	41	(95)	125
Ending balance	102	61	156
Retirement Plans Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(5,014)	(2,706)	(2,471)
Other comprehensive gain (loss)	1,092	(2,308)	(235)
Ending balance	$ (3,922)	$ (5,014)	$ (2,706)