Asset Impairments (Components of Asset Impairments) (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment charges	$ 319		$ 5,851	$ 4,851	$ 15,479
U.S. Oil And Gas Assets [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment charges	317		4,715	2,810	14,340
Canada Oil And Gas Assets [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment charges			336	1,166	336
Other Assets [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment charges	$ 2		1	2	4
General Partner And EnLink [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Goodwill, impairment loss		$ 873	576	$ 873	576
Impairment of intangible assets			$ 223		$ 223