Derivative and Hedging Activities Derivative and Hedging Activities - Marketing, Gathering and Compression Revenues (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Marketing, gathering and compression revenues	$ 1,002	$ 1,219	$ 2,286	$ 2,159
Losses on undesignated supply contract derivatives	0	(37)	0	(17)
Total marketing, gathering and compression revenues	$ 1,002	$ 1,182	$ 2,286	$ 2,142