Acquisitions and Divestitures (Details) (USD $)	3 Months Ended	12 Months Ended
	Jun. 30, 2011	Dec. 31, 2011 MMBtu		Dec. 31, 2011 Exit from Ecuador [Member]	Dec. 31, 2010 Sale of Onshore U.S. Assets [Member]	Dec. 31, 2011 Business Acquisition Dj Basin [Member]
Acquisitions and Divestitures [Abstract]
Interest in joint venture partnership (in hundredths)		50.00%
Undeveloped acres purchased (in acres)		628,000
Approximate purchase price of joint venture partnership		$ 1,300,000,000
Cash paid to date of joint venture partnership		596,000,000
Installments to purchase joint venture partnership		2
Funding agreement for future drilling and completion costs, description		(we 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 approximately eight years or more. The CONSOL Carried Cost Obligation 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. The carry terms ensure economic alignment with our partner in periods of low natural gas prices)
Future drilling and completion costs, maximum		2,100,000,000
Cost Obligation expected term (in years)		8Y
Calendar year funding of future drilling and completion costs, maximum		400,000,000
Natural gas price agreed upon benchmark, average (in MMBtu)		4.00
Total Purchase Price [Abstract]
Unproved Oil and Gas Properties		853,000,000
Proved Oil and Gas Properties		386,000,000
Investment in CONE Gathering LLC		69,000,000
Total		1,308,000,000	[1]			498,000,000
DJ Basin Asset Acquisition						458,000,000
Net Liabilities Assumed						40,000,000
Total		1,308,000,000	[1]			498,000,000
Allocation of Total Purchase Price [Abstract]
Proved Oil and Gas Properties						352,000,000
Unproved Oil and Gas Properties						146,000,000
Total		1,308,000,000	[1]			498,000,000
Gathering and marketing agreement, term (in years)		50 Y
Minimum annual revenue commitment fee (MARC), 2011		3,000,000
Divestitures [Abstract]
Cash proceeds for transfer of assets				73,000,000
Cash Proceeds for sale of onshore US assets					552,000,000
Less [Abstract]
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					3,000,000
Gain on Asset Sale	$ 25,000,000			$ 25,000,000	$ 110,000,000
Working interest terminated by the government of Ecuador				100.00%

[1] Total reflects impact of discount on CONSOL installment payments.