Oil and Gas Exploration and Production Industries Disclosures, Average Sales Price (Details)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Production costs per barrel of oil equivalent	5.85	6.03	4.85
United States [Member]
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Production costs per barrel of oil equivalent	5.96	6.19	5.00
Canada [Member]
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Production costs per barrel of oil equivalent	16.42	14.26	10.28
Trinidad [Member]
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Production costs per barrel of oil equivalent	0.98	0.78	0.65
Other International [Member]
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Production costs per barrel of oil equivalent	18.97	13.82	9.34