Accounting For Certain Long-Lived Assets (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Impaired Long-Lived Assets Held and Used [Line Items]
Amortization Unproved Properties Including Capitalized Interest	$ 228	$ 197	$ 217
United States [Member]
Schedule of Impaired Long-Lived Assets Held and Used [Line Items]
Pretax impairment charges on proved oil and gas properties and other property, plant and equipment	171	403	107
Canada [Member]
Schedule of Impaired Long-Lived Assets Held and Used [Line Items]
Pretax impairment charges on proved oil and gas properties and other property, plant and equipment	872	428	418
Trinidad [Member]
Schedule of Impaired Long-Lived Assets Held and Used [Line Items]
Pretax impairment charges on proved oil and gas properties and other property, plant and equipment			1
Other International [Member]
Schedule of Impaired Long-Lived Assets Held and Used [Line Items]
Pretax impairment charges on proved oil and gas properties and other property, plant and equipment		$ 3