Derivative and Hedging Activities - Marketing, Gathering and Compression Revenues (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Gains on undesignated oil, natural gas and NGL derivatives	$ 5	$ (34)
Total oil, natural gas and NGL revenues	8,595	10,030	$ 10,039
Marketing, gathering and compression | Supply contract
Derivative [Line Items]
Gains on undesignated oil, natural gas and NGL derivatives	(4)	7	0
Marketing
Derivative [Line Items]
Total oil, natural gas and NGL revenues	3,967	5,076	4,511
Marketing | Marketing, gathering and compression
Derivative [Line Items]
Revenues	$ 3,971	$ 5,069	$ 4,511