Asset Impairments (Schedule of Asset Impairments) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment charges	$ 3,035	$ 5,460
U.S. Oil And Gas Assets [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment charges	1,608	5,458
Canada Oil And Gas Assets [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment charges	554
Other Assets [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment charges		$ 2
General Partner And EnLink [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Goodwill, impairment loss	$ 873