Valuation and Qualifying Accounts (Details) (USD $) In Millions	12 Months Ended
	May 31, 2011		May 31, 2010		May 31, 2009
Allowance For Doubtful Accounts Member
Movement In Valuation Allowances And Reserves Roll Forward
Valuation Allowances And Reserves Balance	$ 93		$ 114		$ 88
Charged To Expenses	152		124		181
Deductions	148	[1]	145	[1]	155	[1]
Valuation Allowances And Reserves Balance	97		93		114
Allowance For Revenue Adjustments Member
Movement In Valuation Allowances And Reserves Roll Forward
Valuation Allowances And Reserves Balance	73		82		70
Charged To Other Accounts	532	[2]	430	[2]	466	[2]
Deductions	520	[3]	439	[3]	454	[3]
Valuation Allowances And Reserves Balance	85		73		82
Inventory Valuation Allowance Member
Movement In Valuation Allowances And Reserves Roll Forward
Valuation Allowances And Reserves Balance	170		175		163
Charged To Expenses	13		12		15
Deductions	14		17		3
Valuation Allowances And Reserves Balance	$ 169		$ 170		$ 175

[1] (a) Uncollectible accounts written off, net of recoveries.

[2] (b) Principally charged against revenue.

[3] (c) Service failures, rebills and other.