Accounting For Certain Long-Lived Assets (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Impaired Long-Lived Assets Held and Used [Line Items]
Amortization and impairments of unproved oil and gas property costs including amortization of capitalized interest	$ 168	$ 115	$ 228
United States [Member]
Schedule of Impaired Long-Lived Assets Held and Used [Line Items]
Pretax impairment charges on proved oil and gas properties, other property, plant and equipment and other assets	171	73	171
Canada [Member]
Schedule of Impaired Long-Lived Assets Held and Used [Line Items]
Pretax impairment charges on proved oil and gas properties, other property, plant and equipment and other assets	8	76	872
Trinidad [Member]
Schedule of Impaired Long-Lived Assets Held and Used [Line Items]
Pretax impairment charges on proved oil and gas properties, other property, plant and equipment and other assets		14
Other International [Member]
Schedule of Impaired Long-Lived Assets Held and Used [Line Items]
Pretax impairment charges on proved oil and gas properties, other property, plant and equipment and other assets	$ 396	$ 9