Supplemental Oil and Gas Information (Narrative) (Details)	12 Months Ended
	Dec. 31, 2014
Reserve Quantities [Line Items]
Percentage of bitumen from total bulk tar sand mined	10.00%
Percentage of bitumen removed by extraction process that is contained within the tar sand	90.00%
Metric tons of oil sand used to produce one barrel of synthetic crude oil	2
Natural gas proved reserves expected to receive sale proceeds, per thousand cubic foot	0.24
Future net cash flows annual discount factor, percentage	10.00%
Minimum [Member]
Reserve Quantities [Line Items]
Catalytic cracking process efficiency level	85.00%
Maximum [Member]
Reserve Quantities [Line Items]
Catalytic cracking process efficiency level	90.00%
Canada [Member] | Synthetic Oil [Member]
Reserve Quantities [Line Items]
Interest in synthetic oil operations at Syncrude in Western Canada, percentage	5.00%
Process of mining tar sands and converting the raw bitumen into a pipeline-quality crude	The high-density core-hole drilling, at a spacing of less than 500 meters (proved area), provides engineering and geologic data needed to estimate the volumes of tar sand in place and its associated bitumen content.
Malaysia [Member] | Oil Reserves [Member]
Reserve Quantities [Line Items]
Oil and natural gas reserves associated with the production sharing contracts	94.6
Malaysia [Member] | Natural Gas Reserves [Member]
Reserve Quantities [Line Items]
Oil and natural gas reserves associated with the production sharing contracts	635,600,000,000
Malaysia [Member] | Natural Gas Reserves [Member] | Kikeh Field [Member]
Reserve Quantities [Line Items]
Oil and natural gas reserves associated with the production sharing contracts	54,700,000,000