Acquisitions and Divestitures (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Operating expenses    
Income from discontinued operations, net of tax $ 0 $ 10
Arklatex Area, South Louisiana Wilcox Area, And Brazilian Operations    
Summary of operating results of discontinued operations    
Operating revenues   31
Operating expenses    
Transportation costs   3
Lease operating expense   13
Depreciation, depletion and amortization   6
Impairment charges   3
Other expense   5
Total operating expenses   30
Gain on sale of assets   13
Other income   3
Income from discontinued operations before income taxes   17
Income tax expense   7
Income from discontinued operations, net of tax   10
Brazilian operations    
Operating expenses    
Impairment charges   $ 3