Property, Plant and Equipment - Components of Property, Plant and Equipment (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Total — at cost	$ 33,222	$ 32,504
Less: Reserves for depreciation, depletion, amortization and lease impairment	17,139	16,312
Property, plant and equipment — net	16,083	16,192
Exploration and Production
Property Plant And Equipment [Line Items]
Unproved properties	394	520
Proved properties	3,124	3,162
Wells, equipment and related facilities	26,173	25,550
Total — at cost	29,691	29,232
Midstream
Property Plant And Equipment [Line Items]
Total — at cost	3,492	3,219
Corporate and Other
Property Plant And Equipment [Line Items]
Total — at cost	$ 39	$ 53