Income Taxes (Details 6) (USD $) In Millions	12 Months Ended
	May 31, 2011	May 31, 2010	May 31, 2009
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns Roll Forward
Balance at beginning of year	$ 82	$ 72	$ 88
Increases for tax positions taken in the current year	2	3	7
Increases for tax positions taken in prior years	6	14	10
Decreases for tax positions taken in prior years	(10)	(4)	(30)
Settlements	(11)	(3)	(3)
Balance at end of year	$ 69	$ 82	$ 72