v2.4.0.6
Supplemental Information On Oil And Gas Operations (Costs Incurred) (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
U.S. Onshore [Member]
      
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]      
Property acquisition costs, proved properties $ 34 $ 29 $ 17
Property acquisition costs, unproved properties 851 592 52
Exploration costs 272 339 122
Development costs 4,130 3,126 2,011
Costs incurred 5,287 4,086 2,202
U.S. Offshore [Member]
      
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]      
Property acquisition costs, proved properties       
Property acquisition costs, unproved properties    2 11
Exploration costs    89 260
Development costs    297 537
Costs incurred    388 808
Total U.S [Member]
      
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]      
Property acquisition costs, proved properties 34 29 17
Property acquisition costs, unproved properties 851 594 63
Exploration costs 272 428 382
Development costs 4,130 3,423 2,548
Costs incurred 5,287 4,474 3,010
Canada [Member]
      
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]      
Property acquisition costs, proved properties 14 4 18
Property acquisition costs, unproved properties 88 590 72
Exploration costs 266 260 152
Development costs 1,288 1,216 835
Costs incurred 1,656 2,070 1,077
North America [Member]
      
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]      
Property acquisition costs, proved properties 48 33 35
Property acquisition costs, unproved properties 939 1,184 135
Exploration costs 538 688 534
Development costs 5,418 4,639 3,383
Costs incurred $ 6,943 $ 6,544 $ 4,087