Summary Of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2011 years
Summary Of Significant Accounting Policies [Line Items]
Estimated service life of the asset refineries, in years	25
Estimated service life of other major assets, in years	20
Amortization of computer software development costs, in years	15
Amortization of customer lists, in years	10
Kearl Project [Member]
Summary Of Significant Accounting Policies [Line Items]
Undivided interest in oil and gas activities	70.96%
Syncrude Joint Venture [Member]
Summary Of Significant Accounting Policies [Line Items]
Undivided interest in oil and gas activities	25.00%
Sable Offshore Energy [Member]
Summary Of Significant Accounting Policies [Line Items]
Undivided interest in oil and gas activities	9.00%