Asset Impairments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment charges	$ 7	$ 3,035
General Partner And EnLink [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Goodwill, impairment loss		873
U.S. Oil And Gas Assets [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment charges		1,600
Canada Oil And Gas Assets [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment charges		$ 554