Financing Arrangements - Additional Information (Details) - USD ($)	3 Months Ended	6 Months Ended
Nov. 30, 2018	Nov. 30, 2018	May 31, 2018
Line Of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date	Nov. 13, 2020
Letter of Credit Maximum Sublimit Amount	$ 500,000,000	$ 500,000,000
Financial Covenant Terms Ratio	350.00%	350.00%
Financial Covenant Compliance Ratio	210.00%	210.00%
Commercial paper outstanding	$ 250,000,000	$ 250,000,000
Letters Of Credit Outstanding	54,000,000	54,000,000
Long Term Debt Exclusive of Capital Leases Carrying Value	16,900,000,000	16,900,000,000	$ 16,500,000,000
Long Term Debt Exclusive Of Capital Leases Fair Value	$ 16,200,000,000	$ 16,200,000,000	$ 16,600,000,000
Long-term debt weighted-average interest rate	3.50%	3.50%
Maximum [Member]
Line Of Credit Facility [Line Items]
Commercial paper outstanding	$ 600,000,000	$ 600,000,000
Revolving Credit Facility [Member]
Line Of Credit Facility [Line Items]
Line of Credit Facility, Term	5 years
Line Of Credit Facility Maximum Borrowing Capacity	$ 2,000,000,000	2,000,000,000
Line of credit facility outstanding for future borrowings	1,696,000,000	1,696,000,000
Senior Unsecured Debt [Member]
Line Of Credit Facility [Line Items]
Debt instrument, face amount	1,250,000,000	$ 1,250,000,000
Debt instrument, frequency of interest payment		semi-annually
4.20% Fixed-rate Notes Due in October 2028 [Member]
Line Of Credit Facility [Line Items]
Debt instrument, face amount	$ 400,000,000	$ 400,000,000
Fixed interest rate	4.20%	4.20%
Debt instrument, maturity date	Oct. 17, 2028
4.95% Fixed-rate Notes Due in October 2048 [Member]
Line Of Credit Facility [Line Items]
Debt instrument, face amount	$ 850,000,000	$ 850,000,000
Fixed interest rate	4.95%	4.95%
Debt instrument, maturity date	Oct. 17, 2048
8.000% Notes Due January 15, 2019 [Member]
Line Of Credit Facility [Line Items]
Debt instrument, face amount	$ 750,000,000	$ 750,000,000
Fixed interest rate	8.00%	8.00%
Debt instrument, maturity date	Jan. 15, 2019

Debt divided by adjusted EBITDA

No definition available.

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- Definition

Debt divided by adjusted EBITDA required by the financial covenant.

+ References

No definition available.

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- Definition

Letter of credit maximum sublimit amount.

+ References

No definition available.

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- Definition

Carrying value as of the balance sheet date of long-term unsecured obligations issued by corporations and other borrowers to investors (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion.

+ References

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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Description of the frequency of periodic payments (monthly, quarterly, annual).

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

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- Definition

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.

+ References

No definition available.

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

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- Definition

The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

+ References

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- Definition

Weighted average interest rate of long-term debt outstanding calculated at point in time.

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