Debt (Details) (USD $)					9 Months Ended		12 Months Ended		9 Months Ended							9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2013		Dec. 31, 2012		Sep. 30, 2013 Credit Facility due October 3, 2018 [Member]		Dec. 31, 2012 Credit Facility due October 3, 2018 [Member]		Sep. 30, 2013 CONSOL Installment Payment, due September 30, 2013		Sep. 30, 2012 CONSOL Installment Payment, due September 30, 2013	Dec. 31, 2012 CONSOL Installment Payment, due September 30, 2013		Sep. 30, 2013 FPSO and Other Capital Lease Obligations	Dec. 31, 2012 FPSO and Other Capital Lease Obligations	Sep. 30, 2013 5¼% Senior Notes, due April 15, 2014	Dec. 31, 2012 5¼% Senior Notes, due April 15, 2014	Sep. 30, 2013 8¼% Senior Notes, due March 1, 2019	Dec. 31, 2012 8¼% Senior Notes, due March 1, 2019	Sep. 30, 2013 4.15% Senior Notes, due December 15, 2021	Dec. 31, 2012 4.15% Senior Notes, due December 15, 2021	Sep. 30, 2013 7¼% Senior Notes, due October 15, 2023	Dec. 31, 2012 7¼% Senior Notes, due October 15, 2023	Sep. 30, 2013 8% Senior Notes, due April 1, 2027	Dec. 31, 2012 8% Senior Notes, due April 1, 2027	Sep. 30, 2013 6% Senior Notes, due March 1, 2041	Dec. 31, 2012 6% Senior Notes, due March 1, 2041	Sep. 30, 2013 7¼% Senior Debentures, due August 1, 2097	Dec. 31, 2012 7¼% Senior Debentures, due August 1, 2097
Debt Instrument [Line Items]
Debt	$ 4,614,000,000		$ 4,123,000,000		$ 800,000,000	[1]	$ 0	[1]	$ 0			$ 328,000,000		$ 330,000,000	$ 311,000,000	$ 200,000,000	$ 200,000,000	$ 1,000,000,000	$ 1,000,000,000	$ 1,000,000,000	$ 1,000,000,000	$ 100,000,000	$ 100,000,000	$ 250,000,000	$ 250,000,000	$ 850,000,000	$ 850,000,000	$ 84,000,000	$ 84,000,000
Interest Rate (percentage in hundredths)					1.36%		0.00%		0.00%	[2]		1.79%	[2]	0.00%	0.00%	5.25%	5.25%	8.25%	8.25%	4.15%	4.15%	7.25%	7.25%	8.00%	8.00%	6.00%	6.00%	7.25%	7.25%
Debt instrument, maturity date					Oct. 03, 2018		Oct. 14, 2016		Sep. 30, 2013		Sep. 30, 2013					Apr. 15, 2014	Apr. 15, 2014	Mar. 01, 2019	Mar. 01, 2019	Dec. 15, 2021	Dec. 15, 2021	Oct. 15, 2023	Oct. 15, 2023	Apr. 01, 2027	Apr. 01, 2027	Mar. 01, 2041	Mar. 01, 2041	Aug. 01, 2097	Aug. 01, 2097
Unamortized Discount	(11,000,000)		(15,000,000)
Total Debt, Net of Discount	4,603,000,000		4,108,000,000
Current Portion of Long Term Debt, net of discount	200,000,000	[3]	324,000,000	[3]					0			(324,000,000)				(200,000,000)	0
FPSO and Other Capital Lease Obligations, Current, net of discount														(51,000,000)	(48,000,000)
Long-term Debt Due After One Year	4,352,000,000		3,736,000,000
Revolving Credit Facility Maximum Borrowing Capacity					$ 4,000,000,000

[1] Our Credit Agreement provides for a $4.0 billion unsecured revolving credit facility (Credit Facility), which is available for general corporate purposes.

[2] Imputed rate based on the prevailing market rates for similar debt instruments at the date of assessment.

[3] See Note 5. Debt