Property, Plant and Equipment - Components of Property, Plant and Equipment (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total — at cost	$ 30,519	$ 35,820
Less: Reserves for depreciation, depletion, amortization and lease impairment	16,404	19,006
Property, plant and equipment, net	14,115	16,814
Exploration and Production
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	7,273	9,172
Operating Segments | Exploration and Production
Property, Plant and Equipment [Line Items]
Unproved properties	164	168
Proved properties	2,930	3,304
Wells, equipment and related facilities	23,224	28,404
Total — at cost	26,318	31,876
Operating Segments | Midstream
Property, Plant and Equipment [Line Items]
Total — at cost	4,163	3,904
Corporate, Interest and Other
Property, Plant and Equipment [Line Items]
Total — at cost	38	40
Property, plant and equipment, net	$ 11	$ 12