Revenue - Summary of Revenue from Contracts with Customers on a Disaggregated Basis (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	$ 1,841		$ 4,802
Other operating revenue, includes gains (losses) on commodity derivatives	(48)		(129)
Total sales and other operating revenues	1,793	$ 1,348	4,673	$ 3,803
Exploration and Production
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	1,841		4,802
Other operating revenue, includes gains (losses) on commodity derivatives	(48)		(129)
Total sales and other operating revenues	1,793		4,673
Exploration and Production | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	1,442		3,698
Other operating revenue, includes gains (losses) on commodity derivatives	(48)		(129)
Total sales and other operating revenues	1,394		3,569
Exploration and Production | Europe
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	57		114
Other operating revenue, includes gains (losses) on commodity derivatives	0		0
Total sales and other operating revenues	57		114
Exploration and Production | Africa
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	135		405
Other operating revenue, includes gains (losses) on commodity derivatives	0		0
Total sales and other operating revenues	135		405
Exploration and Production | Asia
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	207		585
Other operating revenue, includes gains (losses) on commodity derivatives	0		0
Total sales and other operating revenues	207		585
Midstream
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	184		527
Other operating revenue, includes gains (losses) on commodity derivatives	0		0
Total sales and other operating revenues	184		527
Midstream | Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	184		527
Crude Oil Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	1,017		2,634
Crude Oil Revenue | Exploration and Production
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	1,017		2,634
Crude Oil Revenue | Exploration and Production | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	826		2,111
Crude Oil Revenue | Exploration and Production | Europe
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	54		106
Crude Oil Revenue | Exploration and Production | Africa
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	108		317
Crude Oil Revenue | Exploration and Production | Asia
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	29		100
Natural Gas Liquids Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	90		236
Natural Gas Liquids Revenue | Exploration and Production
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	90		236
Natural Gas Liquids Revenue | Exploration and Production | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	90		236
Natural Gas Liquids Revenue | Exploration and Production | Europe
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0		0
Natural Gas Liquids Revenue | Exploration and Production | Africa
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0		0
Natural Gas Liquids Revenue | Exploration and Production | Asia
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0		0
Natural Gas Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	230		619
Natural Gas Revenue | Exploration and Production
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	230		619
Natural Gas Revenue | Exploration and Production | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	44		120
Natural Gas Revenue | Exploration and Production | Europe
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	3		8
Natural Gas Revenue | Exploration and Production | Africa
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	5		20
Natural Gas Revenue | Exploration and Production | Asia
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	178		471
Sales of Purchased Oil and Gas
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	504		1,313
Sales of Purchased Oil and Gas | Exploration and Production
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	504		1,313
Sales of Purchased Oil and Gas | Exploration and Production | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	482		1,231
Sales of Purchased Oil and Gas | Exploration and Production | Europe
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0		0
Sales of Purchased Oil and Gas | Exploration and Production | Africa
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	22		68
Sales of Purchased Oil and Gas | Exploration and Production | Asia
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0		14
Sales of Purchased Oil and Gas | Midstream
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0		0
Eliminations
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	(184)		(527)
Other operating revenue, includes gains (losses) on commodity derivatives	0		0
Total sales and other operating revenues	(184)	$ (153)	(527)	$ (454)
Eliminations | Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	(184)		(527)
Eliminations | Sales of Purchased Oil and Gas
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	$ 0		$ 0