Other Noncurrent Assets - Schedule of Other Noncurrent Assets (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Goodwill and Intangible Assets Disclosure [Abstract]
Intangibles, net	$ 737us-gaap_OtherIntangibleAssetsNet	$ 399us-gaap_OtherIntangibleAssetsNet
Cash surrender value of life insurance	506	507
Prepaid gas transmission contract	295aa_PrepaidGasTransmissionContract	315aa_PrepaidGasTransmissionContract
Value-added tax receivable	294	339
Deferred mining costs, net	209us-gaap_DeferredCosts	219us-gaap_DeferredCosts
Fair value of derivative contracts	163us-gaap_DerivativeAssetsNoncurrent	220us-gaap_DerivativeAssetsNoncurrent
Advance related to European Commission Matter in Italy	111us-gaap_NontradeReceivablesNoncurrent	126us-gaap_NontradeReceivablesNoncurrent
Unamortized debt expense	65us-gaap_UnamortizedDebtIssuanceExpense	73us-gaap_UnamortizedDebtIssuanceExpense
Prepaid pension benefit	53us-gaap_PrepaidPensionCosts	88us-gaap_PrepaidPensionCosts
Other	326	342
Other assets, noncurrent, total	$ 2,759us-gaap_OtherAssetsNoncurrent	$ 2,628us-gaap_OtherAssetsNoncurrent

Prepaid gas transmission contract.

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- Definition

Carrying amount as of the balance sheet date of amounts which could be received based on the terms of the insurance contract upon surrendering life policies owned by the entity.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.17)

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-Publisher SEC

-Name Regulation S-X (SX)

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-Paragraph 17

-Article 5

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- Definition

Sum of the carrying amounts of deferred costs that are expected to be recognized as a charge against earnings in periods after one year or beyond the normal operating cycle, if longer.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 17

-Article 5

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.10)

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- Definition

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled after one year or the normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

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- Definition

The noncurrent portion of the receivable other than from customers, that is amounts expected to be collected after one year or the normal operating cycle, if longer.

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Amount of other miscellaneous assets expected to be realized or consumed after one year or normal operating cycle, if longer.

+ References

No definition available.

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Aggregate carrying amount, as of the balance sheet date, of noncurrent assets not separately disclosed in the balance sheet. Noncurrent assets are expected to be realized or consumed after one year (or the normal operating cycle, if longer).

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The net carrying amount as of the balance sheet date of other indefinite-lived and finite-lived intangible assets that are not separately presented on the statement of financial position.

+ References

No definition available.

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- Definition

Cumulative employer's contributions in excess of net pension cost recognized, before the adoption of the recognition provisions of FAS 158. Under FAS 158, prepaid pension costs are no longer recognized in the statement of financial position. Note that there is a separate concept for noncurrent assets relating to defined benefit pension and other defined benefit postretirement plans for use under the recognition provisions of FAS 158.

+ References

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-Publisher FASB

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-Topic 715

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- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

+ References

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Carrying amount due after one year of the balance sheet date (or one operating cycle), if longer of value added taxes due either from customers arising from sales on credit terms, or as previously overpaid to tax authorities.

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