Fair Value Measurements and Disclosures, Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Financial Asset Measured at Fair Value on a Nonrecurring Basis [Abstract]
Impaired Oil and Gas Properties	$ 759		$ 144		$ 504
Impaired Investment in Ecuador					100
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Net of Unamortized Discount	4,114	[1]	1,977	[1]
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Net of Unamortized Discount	4,733	[1]	2,302	[1]
Quoted Prices in Active Markets (Level 1) [Member]
Financial Asset Measured at Fair Value on a Nonrecurring Basis [Abstract]
Impaired Oil and Gas Properties	0	[2]	0	[2]	0	[2]
Impaired Investment in Ecuador					0	[2]
Significant Other Observable Inputs (Level 2) [Member]
Financial Asset Measured at Fair Value on a Nonrecurring Basis [Abstract]
Impaired Oil and Gas Properties	0	[2]	0	[2]	0	[2]
Impaired Investment in Ecuador					0	[2]
Significant Unobservable Inputs (Level 3) [Member]
Financial Asset Measured at Fair Value on a Nonrecurring Basis [Abstract]
Impaired Oil and Gas Properties	213	[2]	30	[2]	363	[2]
Impaired Investment in Ecuador					72	[2]
Net Book Value [Member]
Financial Asset Measured at Fair Value on a Nonrecurring Basis [Abstract]
Impaired Oil and Gas Properties	972	[3]	174	[3]	867	[3]
Impaired Investment in Ecuador					$ 172	[3]

[1] Excludes Aseng FPSO lease obligation.

[2] See Note 1. Summary of Significant Accounting Policies - Fair Value Measurements for a description of the fair value hierarchy.

[3] Amount represents net book value at date of assessment