Amount of revenue from transactions with other operating segments of the same entity.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 131

-Paragraph 27

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

Name:	us-gaap_RevenuesFromTransactionsWithOtherOperatingSegmentsOfSameEntity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Segment Information - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Segment Reporting Information [Line Items]
Number of reportable segments			3
Marketing, Gathering And Compression
Segment Reporting Information [Line Items]
Segment Reporting Information, Intersegment Revenue	$ 1,541	$ 1,324	$ 3,877	$ 3,739