Debt (Details) (USD $)	0 Months Ended			9 Months Ended		9 Months Ended				9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended	0 Months Ended
	Oct. 15, 2011	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2011 Credit Facility due December 9 2012 [Member]	Dec. 31, 2010 Credit Facility due December 9 2012 [Member]	Sep. 30, 2011 CONSOL Installment Payments, due September 30, 2012 and 2013 [Member]	Dec. 31, 2010 CONSOL Installment Payments, due September 30, 2012 and 2013 [Member]	Sep. 30, 2011 FPSO Lease Obligation [Member]	Dec. 31, 2010 FPSO Lease Obligation [Member]	Sep. 30, 2011 Senior Notes due April 15, 2014 [Member]	Dec. 31, 2010 Senior Notes due April 15, 2014 [Member]	Sep. 30, 2011 Senior Notes due March 1, 2019 [Member]	Dec. 31, 2010 Senior Notes due March 1, 2019 [Member]	Sep. 30, 2011 Notes, due October 15, 2023 [Member]	Dec. 31, 2010 Notes, due October 15, 2023 [Member]	Sep. 30, 2011 Senior Notes due April 1, 2027 [Member]	Dec. 31, 2010 Senior Notes due April 1, 2027 [Member]	Sep. 30, 2011 Senior Notes due March 1, 2041 [Member]	Dec. 31, 2010 Senior Notes due March 1, 2041 [Member]	Sep. 30, 2011 Senior Notes due August 1, 2097 [Member]	Dec. 31, 2010 Senior Notes due August 1, 2097 [Member]	Sep. 30, 2011 CONSOL [Member]	Oct. 15, 2011 New Line of Credit [Member]
Debt Instrument [Line Items]
Debt		$ 3,891,000,000	$ 2,279,000,000	$ 400,000,000	$ 350,000,000	$ 656,000,000	$ 0	$ 351,000,000	$ 295,000,000	$ 200,000,000	$ 200,000,000	$ 1,000,000,000	$ 1,000,000,000	$ 100,000,000	$ 100,000,000	$ 250,000,000	$ 250,000,000	$ 850,000,000	$ 0	$ 84,000,000	$ 84,000,000
Interest rate (in hundredths)				0.56%	0.57%	1.76%	0.00%	0.00%	0.00%	5.25%	5.25%	8.25%	8.25%	7.25%	7.25%	8.00%	8.00%	6.00%	0.00%	7.25%	7.25%
Debt instrument, maturity date				Dec. 09, 2012						Apr. 15, 2014		Mar. 01, 2019		Oct. 15, 2023		Apr. 01, 2027		Mar. 01, 2041		Aug. 01, 2097
Debt instrument, maturity dates						September 30, 2012 and 2013
Unamortized discount		(29,000,000)	(7,000,000)
Total debt, net of discount		3,862,000,000	2,272,000,000
Less amounts due within one year						(322,000,000)	0	(33,000,000)	0
Long-Term Debt Due After One Year		3,507,000,000	2,272,000,000
Issuance of 6% Senior Notes [Abstract]
Debt offering face amount																		850,000,000
Debt offerings proceeds, net of discount and underwriting fees																		836,000,000
Total debt issuance costs																		9,000,000
Debt issuance proceeds used to repay outstanding indebtedness																		470,000,000
Debt offering closing date																		2011-02-18
CONSOL Installment Payments [Abstract]
Installment payment amount for joint venture partnership																						328,000,000
Debt Principal Payments [Abstract]
2011		0
2012		728,000,000
2013		328,000,000
2014		200,000,000
2015		0
Thereafter		2,284,000,000
Total		3,540,000,000
FPSO Lease Payments [Abstract]
2011		12,000,000
2012		72,000,000
2013		72,000,000
2014		72,000,000
2015		70,000,000
Thereafter		198,000,000
Total		496,000,000
Credit Facility [Abstract]
Credit Facility, description	(New Credit Facility On October 14, 2011, we entered into a credit agreement with certain commercial lending institutions the Credit Agreement which provides for a new 3.0 billion unsecured five-year revolving credit facility the New Credit Facility. The New Credit Facility replaces our 2.1 billion credit facility maturing December 9, 2012. Also on October 14, 2011, we borrowed 400 million under the New Credit Facility, which was used to repay outstanding borrowings under and to terminate the 2.1 billion credit facility. The New Credit Facility i provides for an initial commitment of 3.0 billion with an option to increase the overall commitment amount by up to an additional 1.0 billion, subject to the consent of any increasing lenders, ii will mature on October 14, 2016, iii provides for facility fee rates that range from 12.5 basis points to 30 basis points per year depending upon our credit rating, iv includes sub-facilities for short-term loans and letters of credit up to an aggregate amount of 500 million under each sub-facility and iv provides for interest rates that are based upon the Eurodollar rate plus a margin that ranges from 100 basis points to 145 basis points depending upon our credit rating.)
Credit facility initiation date																							2011-10-14
Revolving credit facility borrowing capacity				2,100,000,000																			3,000,000,000
New Credit Facility maturity date																							2016-10-31
Line of Credit Facility, option to increase, maximum																							1,000,000,000
Credit facility fee rate basis points, minimum (in hundredths)																							0.125%
Credit facility fee rate basis points, maximum (in hundredths)																							0.30%
Credit facility aggregate short-term loans and letters of credit, maximum																							500,000,000
Credit facility interest rate, Eurodollar rate plus, minimum (in hundredths)																							1.00%
Credit facility interest rate, Eurodollar rate plus, maximum (in hundredths)																							1.45%
New Credit Facility, covenant terms	(The Credit Agreement requires that our total debt to capitalization ratio as defined in the Credit Agreement, expressed as a percentage, not exceed 65 at any time. A violation of this covenant could result in a default under the Credit Agreement, which would permit the participating banks to restrict our ability to access the New Credit Facility and require the immediate repayment of any outstanding advances under the New Credit Facility. The Credit Agreement does not restrict the payment of dividends on our common stock, except, if after giving effect thereto, an Event of Default shall have occurred and be continuing or been caused thereby.)
Credit facility covenant term debt to capitalization ratio maximum (in hundredths)																							65.00%
Credit facility draw down																							$ 400,000,000