Acquisitions (Unaudited) Pro Forma Information (Details) (USD $)	3 Months Ended	9 Months Ended
Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Acquisitions [Abstract]
Business Acquisition, Pro Forma Revenues	$ 6,165,000,000	$ 5,406,000,000	$ 17,190,000,000	$ 16,955,000,000
Business Acquisition, Pro Forma Operating Income	1,707,000,000	1,575,000,000	4,617,000,000	5,081,000,000
Business Acquisition, Pro Forma Income from Continuing Operations	1,048,000,000	898,000,000	2,762,000,000	3,161,000,000
Business Acquisition, Pro Forma Net Income	821,000,000	573,000,000	2,213,000,000	2,397,000,000
Business Acquisition, Pro Forma Earnings Per Share, Basic	$ 0.79	$ 0.55	$ 2.13	$ 2.30
Business Acquisition, Pro Forma Earnings Per Share, Diluted	$ 0.79	$ 0.55	$ 2.12	$ 2.29
Business Combination, Acquisition Related Costs	519,000,000
Income Tax Expense (Benefit), Changes in Deferred Tax Liabilities and Deferred Tax Asset Valuation Allowances			183,000,000
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain	0	0	128,000,000	0
Gain (Loss) on Sale of Oil and Gas Property, Excluded for Full Cost Accounting			$ 77,000,000

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The pro forma operating income (loss), for the period as if the business combination or combinations had been completed at the beginning of a period.

+ References

No definition available.

+ Details

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- Definition

Income tax expense (benefit) related to changes in deferred tax liabilities and deferred tax asset valuation allowances.

+ References

No definition available.

+ Details

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- Definition

The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (h)(2)-(3)

-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463

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- Definition

The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

+ References

+ Details

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- Definition

The pro forma income from continuing operations before changes in accounting and extraordinary items, net of tax effect, for the period as if the business combination or combinations had been completed at the beginning of a period.

+ References

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- Definition

The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

+ References

+ Details

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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

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- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 25

-Paragraph 23

-URI http://asc.fasb.org/extlink&oid=21917927&loc=d3e1043-128460

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- Definition

In a business combination achieved in stages, this element represents the amount of gain recognized by the entity as a result of remeasuring to fair value the equity interest in the acquiree it held before the business combination.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (g)(2)

-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463

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- Definition

Amount of gain (loss) on sale or disposal of proven and unproven oil and gas properties.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

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