Significant Accounting Policies - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified			12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Stock Options	Dec. 31, 2011 Stock Options Minimum	Dec. 31, 2011 Stock Options Maximum	Dec. 31, 2011 Performance-Based Restricted Stock	Dec. 31, 2011 Restricted Stock and Restricted Stock Units	Dec. 31, 2011 Refining Year	Dec. 31, 2011 Refining Minimum	Dec. 31, 2011 Refining Maximum	Dec. 31, 2011 Gasoline stations and other properties Year	Dec. 31, 2011 Syncrude Minimum	Dec. 31, 2011 Syncrude Maximum
Significant Accounting Policies [Line Items]
Canadian government securities with maturities greater than 90 days at the date of acquisition	$ 532,093	$ 616,558
Depreciable lives, Gasoline stations and other properties, straight-line method, minimum								14			3
Depreciable lives, Gasoline stations and other properties, straight-line method, maximum								25			20
Turnarounds for major processing units									4 years	5 years		2 years	3 years
Stock-based compensation, fair value assumption model			Black-Scholes pricing model			Monte Carlo valuation model
Stock-based compensation, vesting period				2 years	3 years	3 years	3 years