Natural Gas Basis Contracts That are Not Designated for Hedge Accounting (Details) (October 2012 - December 2012 [Member], Basis contracts [Member], USD $) In Millions, unless otherwise specified	Sep. 30, 2012
Natural gas basis contracts not designated for hedge accounting [Abstract]
Derivative Liability, Fair Value, Total	$ 3
Rocky Mountains [Member]
Natural gas basis contracts not designated for hedge accounting [Abstract]
Natural Gas Volumes	1,230,000
Weighted Average Differential	(0.91)
Mid-Continent [Member]
Natural gas basis contracts not designated for hedge accounting [Abstract]
Natural Gas Volumes	4,600,000
Weighted Average Differential	(0.55)

Fair value as of the balance sheet date of derivative instrument not designated as hedging instrument and classified as a liability.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 107

-Paragraph 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624163-113959

Name:	us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant