Derivative and Hedging Activities - Natural Gas and Oil Sales Table (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Oil, natural gas and NGL revenues	$ 3,866	$ 4,767	$ 9,336
Gains (losses) on undesignated oil, natural gas and NGL derivatives	(545)	661	1,055
Gains (losses) on terminated cash flow hedges - oil, natural gas and NGL	(33)	(37)	(37)
Total oil, natural gas and NGL revenues	$ 3,288	$ 5,391	$ 10,354