v2.4.0.6
Supplemental Information On Oil And Gas Operations (Estimated Pretax Cash Flow Information Related To Proved Reserves) (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2011
United States [Member]
  
Pre-Tax Future Net Revenue, Proved Developed Reserves $ 30,473 [1]
Pre-Tax Future Net Revenue, Proved Undeveloped Reserves 5,798 [1]
Pre-Tax Future Net Revenue, Total Proved Reserves 36,271 [1]
Pre-Tax 10% Present Value, Proved Developed Reserves 15,165 [1]
Pre-Tax 10% Present Value, Proved Undeveloped Reserves 1,404 [1]
Pre-Tax 10% Present Value, Total Proved Reserves 16,569 [1]
Canada [Member]
  
Pre-Tax Future Net Revenue, Proved Developed Reserves 7,757 [1]
Pre-Tax Future Net Revenue, Proved Undeveloped Reserves 9,288 [1]
Pre-Tax Future Net Revenue, Total Proved Reserves 17,045 [1]
Pre-Tax 10% Present Value, Proved Developed Reserves 5,830 [1]
Pre-Tax 10% Present Value, Proved Undeveloped Reserves 2,508 [1]
Pre-Tax 10% Present Value, Total Proved Reserves 8,338 [1]
North America [Member]
  
Pre-Tax Future Net Revenue, Proved Developed Reserves 38,230 [1]
Pre-Tax Future Net Revenue, Proved Undeveloped Reserves 15,086 [1]
Pre-Tax Future Net Revenue, Total Proved Reserves 53,316 [1]
Pre-Tax 10% Present Value, Proved Developed Reserves 20,995 [1]
Pre-Tax 10% Present Value, Proved Undeveloped Reserves 3,912 [1]
Pre-Tax 10% Present Value, Total Proved Reserves $ 24,907 [1]
[1] Estimated pre-tax future net revenue represents estimated future revenue to be generated from the production of proved reserves, net of estimated production and development costs and site restoration and abandonment charges. The amounts shown do not give effect to depreciation, depletion and amortization, or to non-property related expenses such as debt service and income tax expense.