Acquisitions and Divestitures (Details) (USD $)	9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010
Significant Acquisitions and Disposals [Line Items]
Interest in joint venture partnership (in hundredths)	50.00%
Cash at closing of joint venture partnership	$ 592,000,000
Divestitures [Abstract]
Cash Proceeds			552,000,000
Less
Net Book Value of Assets Sold			(394,000,000)
Goodwill Allocated to Assets Sold			(61,000,000)
Asset Retirement Obligations Associated with Assets Sold			10,000,000
Other Closing Adjustments			7,000,000
Gain on Asset Sale			114,000,000
Total Purchase Price [Abstract]
Unproved Oil and Gas Properties	790,000,000
Proved Oil and Gas Properties	370,000,000
Investment in CONE Gathering LLC	73,000,000
Total Assets Acquired	1,233,000,000	[1]
CONSOL [Member]
Significant Acquisitions and Disposals [Line Items]
Interest in joint venture partnership (in hundredths)	50.00%
Undeveloped acres purchased (in acres)	628,000
Purchase price of joint venture partnership	1,200,000,000
Installments to purchase joint venture partnership	2
Installment payment amount for joint venture partnership	328,000,000
Funding agreement for future drilling and completion costs, description	we have agreed to fund one-third of CONSOL's 50 working interest share of future drilling and completion costs, up to approximately 2.1 billion CONSOL Carried Cost Obligation. The CONSOL Carried Cost Obligation is expected to extend over an eight-year period. It is capped at 400 million in each calendar year and will be suspended if average Henry Hub natural gas prices fall and remain below 4.00 per MMBtu in any three consecutive month period and will remain suspended until average Henry Hub natural gas prices are above 4.00 per MMBtu for three consecutive months. Therefore, specific payment dates for the funding of the CONSOL Carried Cost Obligation cannot be determined at this time
Future drilling and completion costs, maximum	2,100,000,000
Cost Obligation expected term (in years)	8 Y
Calendar year funding of future drilling and completion costs, maximum	400,000,000
Natural gas price agreed upon benchmark, average (in MMBtu)	4.00
CONE Gathering LLC [Member]
Significant Acquisitions and Disposals [Line Items]
Interest in joint venture partnership (in hundredths)	50.00%
Total Purchase Price [Abstract]
Gathering and marketing agreement, term (in years)	50 Y
Minimum annual revenue commitment fee (MARC), projected 2011	3,000,000
Minimum annual revenue commitment fee (MARC), projected 2012	23,000,000
Ecuador Sale [Member]
Divestitures [Abstract]
Cash proceeds for transfer of assets	73,000,000
Less
Gain on Asset Sale	$ 26,000,000

[1] Total reflects impact of discount on remaining installment payments. See Note 5. Debt.