Significant Accounting Policies - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Stock Options	Dec. 31, 2012 Performance Based Restricted Stock	Dec. 31, 2012 Restricted Stock and Restricted Stock Units	Dec. 31, 2012 Minimum Stock Options	Dec. 31, 2012 Maximum Stock Options	Dec. 31, 2012 Refining Minimum	Dec. 31, 2012 Refining Maximum	Dec. 31, 2012 Gasoline stations and other properties Minimum	Dec. 31, 2012 Gasoline stations and other properties Maximum	Dec. 31, 2012 Syncrude Minimum	Dec. 31, 2012 Syncrude Maximum
Significant Accounting Policies [Line Items]
Canadian government securities with maturities greater than 90 days at the date of acquisition	$ 115,603	$ 532,093
Depreciable lives, straight-line method								14 years	25 years	3 years	20 years
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				3 years	3 years	2 years	3 years