Fair Value Measurements (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Asset Impairment Charges [Abstract]
Impairments of goodwill and long-lived assets, Total	$ 0	$ 1,681	$ 0	$ 1,681
Exploration & Production [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value Inputs Level 3 [Member] | Segment, Continuing Operations [Member] | Oil and Gas Properties [Member] | Barnett Shale and Piceance Highlands Combined [Member]
Assets, Fair Value Disclosure [Abstract]
Property, Plant, and Equipment, Fair Value Disclosure		320		320
Exploration & Production [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value Inputs Level 3 [Member] | Segment, Continuing Operations [Member] | United States [Member]
Assets, Fair Value Disclosure [Abstract]
Goodwill, Fair Value Disclosure		0		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value Inputs Level 3 [Member] | Segment, Continuing Operations [Member]
Assets, Fair Value Disclosure [Abstract]
Assets, Fair Value Disclosure		320		320
Fair Value, Measurements, Nonrecurring [Member] | Segment, Continuing Operations [Member]
Assets, Fair Value Disclosure [Abstract]
Assets, Fair Value Disclosure	0		0
Liabilities, Fair Value Disclosure [Abstract]
Liabilities, Fair Value Disclosure	0	0	0	0
Exploration & Production [Member]
Asset Impairment Charges [Abstract]
Impairment of goodwill		1,003		1,003
Impairments of producing properties and acquired unproved reserves		678		678
Exploration & Production [Member] | Barnett Shale [Member]
Asset Impairment Charges [Abstract]
Impairments of producing properties and acquired unproved reserves				503
Exploration & Production [Member] | Piceance Highlands [Member]
Asset Impairment Charges [Abstract]
Impairments of producing properties and acquired unproved reserves				$ 175
Barnett Shale [Member] | Natural Gas Reserves [Member]
Fair Value Inputs [Abstract]
Derivative, Average Forward Price		4.67		4.67
Barnett Shale [Member] | Natural Gas Reserves [Member] | Proved Reserves [Member]
Fair Value Inputs [Abstract]
Proved Developed and Undeveloped Reserves, Net		227,000,000		227,000,000
Barnett Shale [Member] | Proved Reserves [Member]
Fair Value Inputs [Abstract]
After Tax Discount Rate Of Cash Flow		11.00%		11.00%
Piceance Highlands [Member] | Acquired Unproved Reserves [Member]
Fair Value Inputs [Abstract]
After Tax Discount Rate Of Cash Flow		13.00%		13.00%
Natural Gas Reserves [Member]
Fair Value Inputs [Abstract]
Derivative Average Forward Price Percent Decline				22.00%
Derivative, Average Forward Price		4.65		4.65
Natural Gas Reserves [Member] | Proved Reserves [Member]
Fair Value Inputs [Abstract]
Proved Developed and Undeveloped Reserves, Net		4,400,000,000		4,400,000,000
Proved Reserves [Member]
Fair Value Inputs [Abstract]
After Tax Discount Rate Of Cash Flow		11.00%		11.00%
Probable Reserves [Member]
Fair Value Inputs [Abstract]
After Tax Discount Rate Of Cash Flow		13.00%		13.00%
Possible Reserves [Member]
Fair Value Inputs [Abstract]
After Tax Discount Rate Of Cash Flow		15.00%		15.00%