Property, Plant and Equipment - Capitalized Costs Related to Proved and Unproved Oil and Natural Gas Properties by Area (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Proved	$ 7,388	$ 7,344
Less accumulated depletion	(3,990)	(3,607)
Net capitalized costs for oil and natural gas properties	3,398	3,737
Eagle Ford
Property, Plant and Equipment [Line Items]
Proved	4,266	3,898
Northeastern Utah
Property, Plant and Equipment [Line Items]
Proved	1,331	1,659
Permian
Property, Plant and Equipment [Line Items]
Proved	$ 1,791	$ 1,787