Supplemental Information On Oil And Gas Operations (Oil And Gas Properties Not Subject To Amortization) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Acquisition costs	$ 3,144
Exploration costs	332
Development costs	441
Capitalized interest	65
Total oil and gas properties not subject to amortization	3,982
2011 [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Acquisition costs	894
Exploration costs	234
Development costs	359
Capitalized interest	43
Total oil and gas properties not subject to amortization	1,530
2010 [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Acquisition costs	1,101
Exploration costs	81
Development costs	72
Capitalized interest	22
Total oil and gas properties not subject to amortization	1,276
2009 [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Acquisition costs	112
Exploration costs	6
Development costs	1
Total oil and gas properties not subject to amortization	119
Prior To 2009 [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Acquisition costs	1,037
Exploration costs	11
Development costs	9
Total oil and gas properties not subject to amortization	$ 1,057

- Definition

The capitalized costs incurred during the period (excluded from amortization) in identifying areas that may warrant examination and in examining specific areas that are considered to have prospects of containing oil and gas reserves, including costs of drilling exploratory wells and exploratory-type stratigraphic test wells. Exploration costs may be incurred both before acquiring the related property (sometimes referred to in part as prospecting costs) and after acquiring the property. Principal types of exploration costs, which include depreciation and applicable operating costs of support equipment and facilities and other costs of exploration activities, are: costs of topographical, geographical and geophysical studies, rights of access to properties to conduct those studies, and salaries and other expenses of geologists, geophysical crews, and others conducting those studies. Collectively, these are sometimes referred to as geological and geophysical or "G&G" costs. Exploration costs also include costs of carrying and retaining undeveloped properties, such as delay rentals, ad valorem taxes on properties, legal costs for title defense, the maintenance of land and lease records, dry hole contributions and bottom hole contributions, costs of drilling and equipping exploratory wells and costs of drilling exploratory-type stratigraphic test wells.

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