Derivative and Hedging Activities - Natural Gas and Oil Sales Table (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Oil, natural gas and NGL revenues	$ 1,147	$ 812
Gains (losses) on undesignated oil, natural gas and NGL derivatives	332	192
Losses on terminated cash flow hedges	(10)	(11)
Total oil, natural gas and NGL revenues	$ 1,469	$ 993