Retirement Plans (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended
May 31, 2013	May 31, 2012
Cash And Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	$ 456	$ 618
Actual %	2.00%	4.00%
Target %	0 - 5%	0 - 3%
Quoted Prices In Active Markets Level 1	15	8
Other Observable Inputs Level 2	441	610
U.S. Large Cap Equity
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	5,264	4,248
Actual %	28.00%	25.00%
Quoted Prices In Active Markets Level 1	37	9
Other Observable Inputs Level 2	5,227	4,239
U.S. SMID Cap Equity
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	1,741	1,368
Actual %	9.00%	8.00%
Quoted Prices In Active Markets Level 1	1,741	1,368
International Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	2,271	1,657
Actual %	12.00%	10.00%
Quoted Prices In Active Markets Level 1	1,904	1,395
Other Observable Inputs Level 2	367	262
Private Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	332	402
Actual %	2.00%	2.00%
Unobservable Inputs Level 3	332	402
Total Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target %	35 - 55%	45 - 55%
Corporate Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	4,972	4,565
Actual %	26.00%	27.00%
Other Observable Inputs Level 2	4,972	4,565
Government Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	3,888	4,175
Actual %	20.00%	24.00%
Other Observable Inputs Level 2	3,888	4,175
Mortgage Backed And Other Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	200	59
Actual %	1.00%
Other Observable Inputs Level 2	200	59
Total Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target %	45 - 65%	45 - 55%
Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	(77)	(79)
Quoted Prices In Active Markets Level 1	(83)	(85)
Other Observable Inputs Level 2	6	6
Total Asset Class [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	19,047	17,013
Actual %	100.00%	100.00%
Quoted Prices In Active Markets Level 1	3,614	2,695
Other Observable Inputs Level 2	15,101	13,916
Unobservable Inputs Level 3	$ 332	$ 402

This item represents the amount of assets or liabilities, including financial instruments, which are measured at fair value on either a recurring or nonrecurring basis and fall within Level 2 of the fair value measurements hierarchy. Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs include the following: (a) quoted prices for similar assets or liabilities in active markets; (b) quoted prices for identical or similar assets or liabilities in markets that are not active, that is, markets in which there are few transactions for the asset or liability, the prices are not current, or price quotations vary substantially either over time or among market makers (for example, some brokered markets), or in which little information is released publicly (for example, a principal-to-principal market); (c) inputs other than quoted prices that are observable for the asset or liability (for example, interest rates and yield curves observable at commonly quoted intervals, volatilities, prepayment speeds, loss severities, credit risks, and default rates); or (d) inputs that are derived principally from or corroborated by observable market data by correlation or other means (market-corroborated inputs).

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Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

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- Definition

Description of target allocation percentages, or range of percentages, considering the major categories of plan assets as of the latest statement of financial position presented (on a weighted-average basis for employers with more than one plan) that are pertinent to an understanding of the plan investment policies and strategies.

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