Discontinued Operations - Additional Information (Detail) (HighMount [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
HighMount [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment of natural gas and oil properties	$ 29	$ 291	$ 680
Impairment of natural gas and oil properties after tax	19	186	433
Effects of cash flow hedges not considered in calculating ceiling limitation, impairments	29	301	737
Effects of cash flow hedges not considered in calculating ceiling limitation after tax, impairments	18	192	469
Impairment of goodwill before tax		584
Impairment of goodwill after tax		$ 382

Disposal Group Including Discontinued Operation Expenses Impairment Of Goodwill

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- Definition

Disposal Group Including Discontinued Operation Expenses Impairment Of Goodwill Net Of Tax

+ References

No definition available.

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- Definition

Disposal Group Including Discontinued Operation Expenses Impairment Of Natural Gas And Oil Properties

+ References

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- Definition

Disposal Group Including Discontinued Operation Expenses Impairment Of Natural Gas And Oil Properties Net Of Tax

+ References

No definition available.

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- Definition

Effects Of Cash Flow Hedges Not Considered In Calculating Ceiling Limitation Amount Net Of Tax

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No definition available.

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- Definition

Amount that would have been charged to income had the effects of the cash flow hedges not been considered in calculating the ceiling limitation at an oil and gas producing company subject to the full cost rules.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 360

-Section S99

-Paragraph 2

-Subparagraph (SAB TOPIC 12.D.3(b))

-URI http://asc.fasb.org/extlink&oid=27015634&loc=d3e516453-122869

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-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 12

-Section D

-Paragraph b

-Subsection 3

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