Derivatives - Marketing Derivatives and Warrants (Details) $ / shares in Units, shares in Millions, $ in Millions	6 Months Ended					12 Months Ended
	Jun. 30, 2020	Jun. 30, 2020 $ / Barrel	Jun. 30, 2020 $ / MillionCubicFeet	Jun. 30, 2020 MMBbls	Jun. 30, 2020 Bcf	Dec. 31, 2019 $ / Barrel	Dec. 31, 2019 $ / MillionCubicFeet	Dec. 31, 2019 MMBbls	Dec. 31, 2019 Bcf	Jun. 26, 2020 $ / shares shares	May 29, 2020 USD ($)	Aug. 08, 2019 $ / shares shares
Marketing Derivatives
Outstanding commodity derivatives contracts not designated as hedging instruments
Derivative instrument settlement period (within)	3 months
Marketing Derivatives | Not designated as hedging instruments
Outstanding commodity derivatives contracts not designated as hedging instruments
Weighted average sales price (dollars per barrel)		36.24	1.55			60.60	2.17
Crude oil | Not designated as hedging instruments | Long position
Outstanding commodity derivatives contracts not designated as hedging instruments
Outstanding net volumes on derivatives not designated as hedges (mmbls/bcf)				28	(131)			55	(128)
Common Stock
Outstanding commodity derivatives contracts not designated as hedging instruments
Warrants issued (in shares) | shares										3.9
Exercise price of warrant (usd per share) | $ / shares										$ 59.624
Additional Paid-in Capital | Reclassification
Outstanding commodity derivatives contracts not designated as hedging instruments
Fair value of warrant, reclassification | $											$ 102
Anadarko | Common Stock
Outstanding commodity derivatives contracts not designated as hedging instruments
Warrants issued (in shares) | shares												80.0
Exercise price of warrant (usd per share) | $ / shares												$ 62.50