Impairments - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Property, Plant and Equipment [Line Items]
Impairment of Oil and Natural Gas Properties	$ 0	$ 497	$ 0	$ 2,564
Impairments of Fixed Assets and Other	9	751	426	795
Loss on Transportation Agreement	$ 978	1,261	3,333	$ 3,410
Other, Barnett Shale Exit Costs,Termination of Gathering Agreement [Member]
Property, Plant and Equipment [Line Items]
Impairments of Fixed Assets and Other		334
Other, Barnett Shale Exit Costs, Other Property and Equipment [Member]
Property, Plant and Equipment [Line Items]
Impairments of Fixed Assets and Other		282
Exploration and Production Equipment, Buildings and Land, Devonian Shale [Member]
Property, Plant and Equipment [Line Items]
Impairments of Fixed Assets and Other		$ 134
Transportation Equipment [Member] | Natural Gas [Member]
Property, Plant and Equipment [Line Items]
Loss on Contract Termination			126
Transportation Equipment [Member] | Oil [Member]
Property, Plant and Equipment [Line Items]
Loss on Transportation Agreement			$ 290