Date when the debt instrument is scheduled to be fully repaid, which may be presented in a variety of ways (year, month and year, day, month and year, quarter, etc.).

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(2))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

The average forward price on the group of price risk forward or futures contracts, such as gas futures contracts.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Unrealized Fair Value Adjustments on Derivative Financial Instruments

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Unrealized Fair Value Adjustments on Derivative Financial Instruments

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- Definition

Volume Of Future Oil And Gas Production Being Hedged

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- Definition

Represents the amount of equivalent Mcfe production our derivative financial instruments covered.

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Derivative Financial Instruments (Narrative) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended										3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011 Interest Rate Swaps [Member]	Sep. 30, 2010 Interest Rate Swaps [Member]	Sep. 30, 2011 Remainder Of 2011 [Member] Natural Gas [Member]	Sep. 30, 2011 Remainder Of 2011 [Member] Oil [Member]	Sep. 30, 2011 2012 [Member] Natural Gas [Member]	Sep. 30, 2011 2012 [Member] Oil [Member]	Dec. 31, 2010 Natural Gas [Member] MMcf	Dec. 31, 2010 Oil [Member] MBbls	Sep. 30, 2011 Commodity Contracts [Member]	Sep. 30, 2010 Commodity Contracts [Member]	Sep. 30, 2011 Commodity Contracts [Member]	Sep. 30, 2010 Commodity Contracts [Member]
Derivative [Line Items]
Unrealized fair value adjustments included in Gain (loss) on derivative financial instruments													$ 51.4	$ 13.1	$ 47.9	$ (10.6)
Unrealized fair value adjustments included in Interest expense						$ 2.0
Outstanding derivative contracts volume (in Mmcf)											89,500	822
Average forward prices							$ 3.80	$ 79.37	$ 4.24	$ 81.06
Percentage of derivative instruments to equivalent production	63.70%	49.60%	57.60%	56.20%
Debt instrument maturity date					Feb. 14, 2010