Impairments Impairments - Fixed Assets and Other Table (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Impairments of Fixed Assets and Other	$ 421	$ 838	$ 194
Other, Barnett Shale Exit Costs [Member]
Property, Plant and Equipment [Line Items]
Impairments of Fixed Assets and Other	0	645	0
Other Devonian Shale Exit Costs [Member]
Property, Plant and Equipment [Line Items]
Impairments of Fixed Assets and Other	0	142	0
Exploration and Production Equipment [Member]
Property, Plant and Equipment [Line Items]
Impairments of Fixed Assets and Other	0	3	173
Gas Gathering and Processing Equipment [Member]
Property, Plant and Equipment [Line Items]
Impairments of Fixed Assets and Other			0
Natural Gas Compressor [Member]
Property, Plant and Equipment [Line Items]
Impairments of Fixed Assets and Other	0	21
Natural Gas Compressors [Member]
Property, Plant and Equipment [Line Items]
Impairments of Fixed Assets and Other			21
Buildings and Land [Member]
Property, Plant and Equipment [Line Items]
Impairments of Fixed Assets and Other	5	11	0
Other [Member]
Property, Plant and Equipment [Line Items]
Impairments of Fixed Assets and Other	$ 416	$ 16	$ 194