Properties and Equipment (Detail) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant, and Equipment [Line Items]
Gross properties and equipment		$ 65,050	$ 69,013
Less accumulated depreciation, depletion, and amortization		37,599	36,845
Net properties and equipment		27,451	32,168	$ 33,751
Exploration and Production Reporting Segment [Member]
Property, Plant, and Equipment [Line Items]
Gross properties and equipment	[1]	52,364	57,581
Costs associated with unproved properties		2,400	4,100
WES Midstream Reporting Segment [Member]
Property, Plant, and Equipment [Line Items]
Gross properties and equipment		7,871	6,862
Other Midstream Reporting Segment [Member]
Property, Plant, and Equipment [Line Items]
Gross properties and equipment		2,012	1,785
Other [Member]
Property, Plant, and Equipment [Line Items]
Gross properties and equipment		$ 2,803	$ 2,785

[1] Includes costs associated with unproved properties of $2.4 billion at December 31, 2017, and $4.1 billion at December 31, 2016.