Derivative and Hedging Activities Derivative and Hedging Activities, Marketing, Gathering and Compression Sales (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Marketing, gathering and compression revenues	$ 1,182	$ 2,305	$ 2,142	$ 3,980
Gains (losses) on undesignated supply contract derivatives	0	0	0	10
Total marketing, gathering and compression revenues	1,182	2,305	2,142	3,980
Marketing, Gathering And Compression [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Marketing, gathering and compression revenues	1,219	2,085	2,159	3,760
Gains (losses) on undesignated supply contract derivatives	(37)	220	(17)	220
Total marketing, gathering and compression revenues	$ 1,219	$ 2,085	$ 2,159	$ 3,760