Supplemental Quarterly Financial Information (Unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2010		Sep. 30, 2010		Jun. 30, 2010		Mar. 31, 2010		Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Quarterly Financial Information [Abstract]
Revenues	$ 985	[1]	$ 924	[1]	$ 954	[1]	$ 899	[1]	$ 783	[2]	$ 755	[2]	$ 751	[2]	$ 733	[2]	$ 3,763	[1],[3]	$ 3,022	[2],[3]	$ 2,313	[3]
Income (Loss) Before Income Taxes	(470)	[1]	722	[1]	425	[1]	37	[1]	69	[2]	298	[2]	320	[2]	343	[2]	715	[1]	1,031	[2]	(264)
Net Income (Loss)	(296)	[1]	441	[1]	294	[1]	14	[1]	52	[2]	232	[2]	204	[2]	237	[2]	453	[1]	725	[2]	(131)
Earnings Per Share [Abstract]
Basic	$ (1.67)	[1],[4]	$ 2.50	[1],[4]	$ 1.66	[1],[4]	$ 0.08	[1],[4]	$ 0.29	[2],[4]	$ 1.33	[2],[4]	$ 1.17	[2],[4]	$ 1.36	[2],[4]	$ 2.57	[1],[4]	$ 4.15	[2],[4]	$ (0.75)
Diluted	$ (1.67)	[1],[4],[5]	$ 2.39	[1],[4],[5]	$ 1.61	[1],[4],[5]	$ 0.08	[1],[4],[5]	$ 0.29	[2],[4]	$ 1.31	[2],[4]	$ 1.10	[2],[4]	$ 1.34	[2],[4]	$ 2.54	[1],[4],[5]	$ 4.10	[2],[4]	$ (0.75)
Asset Impairments	620				131		8		44		100						759		144		604
(Gain) Loss on Commodity Derivative Instruments	137		(322)		(143)		286		122		(38)		(96)		(145)		(42)		(157)		110
Unrealized (Gain) Loss on Commodity Derivative Instruments	162		(300)		(142)		303		145		(5)		(63)		(147)		22		(70)		606
Pre-tax gain on divestitures					25
Rig contract termination expense													26
Gain on sale of non-core onshore US assets											114
Deferred Compensation Arrangements Trust Plan Distribution Amount			$ 12		$ 4								$ 9

[1] First quarter 2011 included the following: $8 million asset impairment charges (See Note 4. Asset Impairments); and $286 million loss on commodity derivative instruments, including unrealized mark-to-market loss of $303 million (See Note 10. Derivative Instruments and Hedging Activities). Second quarter 2011 included the following: $143 million gain on commodity derivative instruments, including unrealized mark-to-market gain of $142 million (See Note 10. Derivative Instruments and Hedging Activities); $25 million pre-tax gain on divestitures due to the completed transfer of assets and exit from Ecuador (See Note 3. Acquisitions and Divestitures); and $131 million asset impairment charges (See Note 4. Asset Impairments). Third quarter 2011 included the following: $322 million gain on commodity derivative instruments, including unrealized mark-to-market gain of $300 million (See Note 10. Derivative Instruments and Hedging Activities). Fourth quarter 2011 included the following: $620 million asset impairment charges (See Note 4. Asset Impairments); and $137 million loss on commodity derivative instruments, including unrealized mark-to-market loss of $162 million (See Note 10. Derivative Instruments and Hedging Activities).

[2] First quarter 2010 included the following: $145 million gain on commodity derivative instruments, including unrealized mark-to-market gain of $147 million (See Note 10. Derivative Instruments and Hedging Activities). Second quarter 2010 included the following: $96 million gain on commodity derivative instruments, including unrealized mark-to-market gain of $63 million (See Note 10. Derivative Instruments and Hedging Activities); and $26 million rig contract termination expense due to the Deepwater Moratorium. Third quarter 2010 included the following: $38 million gain on commodity derivative instruments, including unrealized mark-to-market gain of $5 million (See Note 10. Derivative Instruments and Hedging Activities); $114 million gain on sale of non-core onshore US assets (See Note 3. Acquisitions and Divestitures); and $100 million asset impairment charges (See Note 4. Asset Impairments). Fourth quarter 2010 included the following: $122 million loss on commodity derivative instruments, including unrealized mark-to-market loss of $145 million (See Note 10. Derivative Instruments and Hedging Activities); and $44 million asset impairment charges (See Note 4. Asset Impairments).

[3] Revenues from third parties for all foreign countries, in total, were $1.6 billion in 2011, $1 billion in 2010, and $791 million in 2009.

[4] The sum of the individual quarterly earnings (loss) per share amounts may not agree with year-to-date earnings per share as each quarterly computation is based on the income or loss for that quarter and the weighted average number of shares outstanding during that quarter.

[5] Consistent with GAAP, when dilutive, deferred compensation gains or losses, net of tax, are excluded from net income while the NBL shares held in the rabbi trust are included in the diluted share count. For this reason, the diluted earnings per share calculations for the three months ended June 30 and September 30, 2011 exclude deferred compensation gains of $4 million and $12 million, respectively, net of tax, and for the three months ended June 30, 2010 excludes a deferred compensation gain of $9 million, net of tax.