Debt - Classification and Utilization (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2022	Dec. 31, 2021
Debt
Debt maturing or subject to remarketing within twelve months	$ 3,000
Current portion of long-term debt	435	$ 708
Debt classified as long-term due to intent and ability to refinance on long-term basis	2,600
2.90% senior notes due 2022 [Member]
Debt
Debt maturing or subject to remarketing within twelve months	$ 500
Interest rate (as a percent)	2.90%
Tax Exempt Bonds [Member]
Debt
Debt maturing or subject to remarketing within twelve months	$ 71
Debt with interest rate periods that expire in the next 12 months	645
Variable-rate tax-exempt bonds	54
Variable-rate tax-exempt bonds, non-current	$ 54
Tax Exempt Bonds [Member] \| Minimum [Member]
Debt
Interest rate (as a percent)	0.30%	0.30%
Tax Exempt Bonds [Member] \| Maximum [Member]
Debt
Interest rate (as a percent)	4.30%	4.30%
Financing leases and other [Member]
Debt
Debt maturing or subject to remarketing within twelve months	$ 180
Revolving Credit Facility [Member]
Debt
Maximum capacity	3,500
Outstanding borrowings under credit facility	0
Letters of credit outstanding	166
Unused and available credit capacity	1,600
Commercial Paper Program [Member]
Debt
Debt maturing or subject to remarketing within twelve months	$ 1,700
Debt term	397 days
Commercial paper borrowings	$ 1,700
Other Letter Of Credit Lines [Member]
Debt
Letters of credit outstanding	$ 769

Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

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- Definition

Amount of short-term debt and current maturity of long-term debt and capital lease obligations due within one year or the normal operating cycle, if longer.

+ References

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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

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.

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

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

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 rate subject to change from time to time.

+ References

No definition available.

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- Definition

Amount of short-term borrowings, long-term debt and financing leases due or subject to remarketing within the next twelve months, including amounts classified as current and amounts classified as noncurrent due to intent and ability to refinance.

+ References

No definition available.

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- Definition

Represent debt with interest rate periods that expire within the next 12 months.

+ References

No definition available.

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- Definition

The portion of short-term borrowings, current maturities of long-term debt and capital lease obligations and borrowings subject to refinancing within the next twelve months, classified as long-term obligations due to the intent and ability to refinance on a long-term basis.

+ References

No definition available.

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- Definition

The long-term portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, which accrues interest at a rate subject to change from time to time.

+ References

No definition available.

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