Ownership interest purchased.

No definition available.

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- Definition

Date when the business acquisition agreement was executed, in CCYY-MM-DD format.

+ References

No definition available.

+ Details

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- Details

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- Definition

The amount of property, plant, and equipment recognized as of the acquisition date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6910749&loc=d3e4845-128472

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 55

-Paragraph 37

-URI http://asc.fasb.org/extlink&oid=25498275&loc=d3e2207-128464

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585

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Acquisitions and Divestitures - Acquisitions (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended		1 Months Ended	9 Months Ended	1 Months Ended	9 Months Ended	1 Months Ended	9 Months Ended	1 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Mar. 31, 2013 Marcellus Interest in Gas Gathering Systems [Member] Western Gas Partners, LP [Member]	Sep. 30, 2013 Marcellus Interest in Gas Gathering Systems [Member] Western Gas Partners, LP [Member]	Jun. 30, 2013 Mont Belvieu Joint Venture [Member] Western Gas Partners, LP [Member]	Sep. 30, 2013 Mont Belvieu Joint Venture [Member] Western Gas Partners, LP [Member]	Aug. 31, 2013 Moxa Oil and Gas Properties [Member]	Sep. 30, 2013 Moxa Oil and Gas Properties [Member]	Sep. 30, 2013 Intrastate Pipeline in Wyoming [Member] Western Gas Partners, LP [Member]	Sep. 30, 2013 Intrastate Pipeline in Wyoming [Member] Western Gas Partners, LP [Member]
Business Acquisition [Line Items]
Date of acquisition agreement				Mar. 31, 2013		Jun. 30, 2013		Aug. 31, 2013		Sep. 30, 2013
Ownership interest purchased			33.75%		25.00%
Purchase price	$ 473	$ 0	$ 135		$ 78		$ 310		$ 28
Fair value, oil and gas properties acquired							$ 306