Goodwill and Other Intangible Assets (Details 2) - USD ($) $ in Millions	12 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2013
Goodwill and Other Intangible Assets [Abstract]
Intangible assets amortization expense	$ 21	$ 23	$ 27
Estimated 2016 amortization expense	30
Finite Lived Intangible Assets [Line Items]
Net Book Value	207	$ 57
GENCO intangible [Member]
Finite Lived Intangible Assets [Line Items]
Net Book Value	$ 164