Derivative and Hedging Activities Derivative and Hedging Actitities - Marketing, Gathering and Compression Revenues Table (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Revenues	$ 9,496	$ 7,872	$ 12,764
Marketing, gathering and compression	4,511	4,584	7,373
Marketing, Gathering And Compression [Member]
Derivative [Line Items]
Revenues	4,511	4,881	7,077
Marketing, Gathering And Compression [Member] | Supply Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 0	$ (297)	$ 296