Property, Plant and Equipment - Components of Property, Plant and Equipment (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Property Plant And Equipment [Line Items]
Total — at cost	$ 46,826	$ 46,522
Less: Reserves for depreciation, depletion, amortization and lease impairment	20,474	19,005
Property, plant and equipment, net	26,352	27,517
Exploration and Production
Property Plant And Equipment [Line Items]
Unproved properties	958	1,468
Proved properties	4,202	4,211
Wells, equipment and related facilities	38,738	38,263
Total — at cost	43,898	43,942
Bakken Midstream
Property Plant And Equipment [Line Items]
Total — at cost	2,757	2,386
Property, plant and equipment, net	2,358
Corporate, Interest and Other
Property Plant And Equipment [Line Items]
Total — at cost	$ 171	$ 194