Retirement Plans (Details 4) - USD ($) $ in Millions	12 Months Ended
May. 31, 2015	May. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	$ 23,006	$ 21,444
Quoted Prices In Active Markets Level 1	3,565	3,141
Other Observable Inputs Level 2	19,215	18,027
Unobservable Inputs Level 3	226	276
Cash And Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	$ 738	$ 313
Actual %	3.00%	2.00%
Target %	0 - 5%	0 - 5%
Quoted Prices In Active Markets Level 1	$ 36	$ 55
Other Observable Inputs Level 2	702	258
U.S. Large Cap Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	$ 4,291	$ 5,196
Actual %	19.00%	24.00%
Quoted Prices In Active Markets Level 1	$ 302	$ 55
Other Observable Inputs Level 2	3,989	5,141
U.S. SMID Cap Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	$ 979	$ 886
Actual %	4.00%	4.00%
Quoted Prices In Active Markets Level 1	$ 979	$ 886
International Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	$ 3,064	$ 2,652
Actual %	14.00%	12.00%
Quoted Prices In Active Markets Level 1	$ 2,429	$ 2,206
Other Observable Inputs Level 2	635	446
Global Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	$ 2,579	$ 1,367
Actual %	11.00%	7.00%
Other Observable Inputs Level 2	$ 2,579	$ 1,367
Private Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	$ 226	$ 276
Actual %	1.00%	1.00%
Unobservable Inputs Level 3	$ 226	$ 276
Total Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target %	35 - 55%	35 - 55%
Corporate Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	$ 6,455	$ 5,758
Actual %	28.00%	27.00%
Other Observable Inputs Level 2	$ 6,455	$ 5,758
Government Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	$ 4,645	$ 4,782
Actual %	20.00%	22.00%
Other Observable Inputs Level 2	$ 4,645	$ 4,782
Mortgage Backed And Other Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	$ 213	$ 275
Actual %	1.00%	1.00%
Other Observable Inputs Level 2	$ 213	$ 275
Total Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target %	45 - 65%	45 - 65%
Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	$ (184)	$ (61)
Actual %	(1.00%)
Quoted Prices In Active Markets Level 1	$ (181)	$ (61)
Other Observable Inputs Level 2	$ (3)
Total Asset Class [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual %	100.00%	100.00%

The percentage of the fair value of asset class to the fair value of total plan assets held as of the measurement date.

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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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Section 35

-Paragraph 50

-URI http://asc.fasb.org/extlink&oid=29635418&loc=d3e12355-114930

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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