Outstanding Natural Gas Contracts That Are Not Designated for Hedge Accounting (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012
October 2012 - December 2012 [Member]
Derivative [Line Items]
Derivative, Natural Gas Weighted Average Price	4.04
January 2013 - December 2013 [Member]
Derivative [Line Items]
Derivative, Natural Gas Weighted Average Price	4.85
Natural gas contracts [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Total	$ 33
Three Way collar contracts [Member] \| Natural gas contracts [Member] \| October 2012 - December 2012 [Member]
Derivative [Line Items]
Natural Gas Volumes	15,070,000
Derivative Weighted Average Additional Put Price	4.19
Derivative, Weighted Average Floor Price	5.51
Derivative, Weighted Average Ceiling Price	6.41
Derivative Asset, Fair Value, Total	19
Three Way collar contracts [Member] \| Natural gas contracts [Member] \| October 2012 - December 2012 [Member] \| Maximum [Member]
Derivative [Line Items]
Additional Put Range	4.50
Floor Range	6.00
Ceiling Range	7.55
Three Way collar contracts [Member] \| Natural gas contracts [Member] \| October 2012 - December 2012 [Member] \| Minimum [Member]
Derivative [Line Items]
Additional Put Range	3.50
Floor Range	5.00
Ceiling Range	5.20
Three Way collar contracts [Member] \| Natural gas contracts [Member] \| January 2013 - December 2013 [Member]
Derivative [Line Items]
Natural Gas Volumes	39,530,000
Derivative Weighted Average Additional Put Price	4.04
Derivative, Weighted Average Floor Price	5.44
Derivative, Weighted Average Ceiling Price	6.48
Derivative Asset, Fair Value, Total	42
Three Way collar contracts [Member] \| Natural gas contracts [Member] \| January 2013 - December 2013 [Member] \| Maximum [Member]
Derivative [Line Items]
Additional Put Range	4.50
Floor Range	6.00
Ceiling Range	7.55
Three Way collar contracts [Member] \| Natural gas contracts [Member] \| January 2013 - December 2013 [Member] \| Minimum [Member]
Derivative [Line Items]
Additional Put Range	3.50
Floor Range	5.00
Ceiling Range	6.00
Collar Contracts [Member] \| Natural gas contracts [Member] \| January 2014 - December 2014 [Member]
Derivative [Line Items]
Natural Gas Volumes	14,600,000
Floor Range	3.75
Derivative, Weighted Average Floor Price	3.75
Derivative, Weighted Average Ceiling Price	4.55
Derivative Liability, Fair Value, Total	1
Collar Contracts [Member] \| Natural gas contracts [Member] \| January 2014 - December 2014 [Member] \| Maximum [Member]
Derivative [Line Items]
Ceiling Range	4.57
Collar Contracts [Member] \| Natural gas contracts [Member] \| January 2014 - December 2014 [Member] \| Minimum [Member]
Derivative [Line Items]
Ceiling Range	4.54
Swap [Member] \| Natural gas contracts [Member] \| October 2012 - December 2012 [Member]
Derivative [Line Items]
Natural Gas Volumes	11,340,000
Derivative, Swap Type, Average Fixed Price	3.19
Derivative Asset, Fair Value, Total	1
Swap [Member] \| Natural gas contracts [Member] \| January 2013 - December 2013 [Member]
Derivative [Line Items]
Natural Gas Volumes	54,750,000
Derivative, Swap Type, Average Fixed Price	4.08
Derivative Asset, Fair Value, Total	13
Swap [Member] \| Natural gas contracts [Member] \| January 2014 - December 2014 [Member]
Derivative [Line Items]
Natural Gas Volumes	54,750,000
Derivative, Swap Type, Average Fixed Price	3.85
Derivative Liability, Fair Value, Total	17
Additional Swap [Member] \| Natural gas contracts [Member] \| October 2012 - December 2012 [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price	2.72
Derivative Liability, Fair Value, Total	9
Additional Swap [Member] \| Natural gas contracts [Member] \| January 2013 - December 2013 [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price	3.45
Derivative Liability, Fair Value, Total	$ 15

Additional Put Range

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- Definition

Derivative Average Additional Put Price.

+ References

No definition available.

+ Details

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- Definition

Average realized price rate related to the group of price risk swap and 3 way collar natural gas derivatives.

+ References

No definition available.

+ Details

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- Definition

No authoritative reference available.

+ References

No definition available.

+ Details

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- Definition

The average cap rate on a group of price risk derivatives such as caps or collars. A payment or receipt is triggered if the market rate exceeds the cap rate on the contract.

+ References

No definition available.

+ Details

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- Definition

The average floor rate on a group of price risk derivatives such as floors or collars. A payment or receipt is triggered if the market rate falls below the floor rate on the contract.

+ References

No definition available.

+ Details

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- Definition

The cap rate on a price risk derivative such as a cap or collar. A payment or receipt is triggered if the market rate exceeds the cap rate on the contract.

+ References

No definition available.

+ Details

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- Definition

Floor rate on a price risk derivative such as a floor or a collar. A payment or receipt is triggered if the market rate falls below the floor rate on the contract.

+ References

No definition available.

+ Details

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- Definition

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

+ References

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

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Period Type:	instant

- Definition

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

+ References

+ Details

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- Details

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Period Type:	duration

- Definition

Average fixed price related to the group of price risk swap derivatives.

+ References

No definition available.

+ Details

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