Acquisitions and Divestitures (Details) (Mobil North Sea Limited [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2012
Mobil North Sea Limited [Member]
Assets acquired and liabilities assumed as of the acquisition date
Current assets	$ 208
Oil and gas properties	2,817
Gathering, transmission and processing facilities	338
Goodwill	82
Total assets acquired	3,445
Current liabilities	148
Asset retirement obligation	517
Deferred income tax liabilities	1,533
Other long-term obligations	1
Total liabilities assumed	2,199
Net assets acquired	$ 1,246

Business acquisition purchase price allocation asset retirement obligation.

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- Definition

Business acquisition purchase price allocation gas gathering transmission and procession.

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Business acquisition purchase price allocation noncurrent liabilities deferred income tax liabilities.

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Business acquisition purchase price allocation oil and gas properties.

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- Definition

The amount of acquisition cost of a business combination allocated to assets acquired.

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The total purchase price of the acquired entity. This includes cash paid to equity interest holders of the acquired entity, fair value of debt and equity securities issued to equity holders of the acquired entity, and transaction costs paid to third parties to consummate the acquisition.

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The amount of acquisition cost of a business combination allocated to current assets.

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The amount of acquisition cost of a business combination allocated to current liabilities of the acquired entity.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph 51

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-Publisher FASB

-Name Emerging Issues Task Force (EITF)

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Amount of goodwill arising from a business combination, which is the excess of the cost of the acquired entity over the amounts assigned to assets acquired and liabilities assumed.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph 52

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

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The amount of acquisition cost of a business combination allocated to liabilities assumed.

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The amount of acquisition cost of a business combination allocated to other noncurrent liabilities of the acquired entity.

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