Oil and Gas Exploration and Production Industries Disclosures, Average Sales Price (Details)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
United States [Member]
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Production costs per barrel of oil equivalent	6.19	5.00	4.43
Canada [Member]
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Production costs per barrel of oil equivalent	14.26	10.28	8.41
Trinidad [Member]
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Production costs per barrel of oil equivalent	0.78	0.65	0.74
Other International [Member]
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Production costs per barrel of oil equivalent	13.82	9.34	10.52