Revenue - Summary of Revenue from Contracts with Customers on a Disaggregated Basis (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	$ 1,581		$ 2,961
Other operating revenue, includes gains (losses) on commodity derivatives	(47)		(81)
Total sales and other operating revenues	1,534	$ 1,197	2,880	$ 2,455
Exploration and Production
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	1,581		2,961
Other operating revenue, includes gains (losses) on commodity derivatives	(47)		(81)
Total sales and other operating revenues	1,534		2,880
Exploration and Production | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	1,228		2,256
Other operating revenue, includes gains (losses) on commodity derivatives	(47)		(81)
Total sales and other operating revenues	1,181		2,175
Exploration and Production | Europe
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	21		57
Other operating revenue, includes gains (losses) on commodity derivatives	0		0
Total sales and other operating revenues	21		57
Exploration and Production | Africa
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	139		270
Other operating revenue, includes gains (losses) on commodity derivatives	0		0
Total sales and other operating revenues	139		270
Exploration and Production | Asia
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	193		378
Other operating revenue, includes gains (losses) on commodity derivatives	0		0
Total sales and other operating revenues	193		378
Midstream
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	176		343
Other operating revenue, includes gains (losses) on commodity derivatives	0		0
Total sales and other operating revenues	176		343
Midstream | Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	176		343
Crude Oil Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	849		1,617
Crude Oil Revenue | Exploration and Production
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	849		1,617
Crude Oil Revenue | Exploration and Production | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	692		1,285
Crude Oil Revenue | Exploration and Production | Europe
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	19		52
Crude Oil Revenue | Exploration and Production | Africa
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	110		209
Crude Oil Revenue | Exploration and Production | Asia
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	28		71
Natural Gas Liquids Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	75		146
Natural Gas Liquids Revenue | Exploration and Production
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	75		146
Natural Gas Liquids Revenue | Exploration and Production | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	75		146
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	211		389
Natural Gas Revenue | Exploration and Production
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	211		389
Natural Gas Revenue | Exploration and Production | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	37		76
Natural Gas Revenue | Exploration and Production | Europe
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	2		5
Natural Gas Revenue | Exploration and Production | Africa
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	7		15
Natural Gas Revenue | Exploration and Production | Asia
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	165		293
Sales of Purchased Oil and Gas
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	446		809
Sales of Purchased Oil and Gas | Exploration and Production
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	446		809
Sales of Purchased Oil and Gas | Exploration and Production | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	424		749
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		46
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	(176)		(343)
Other operating revenue, includes gains (losses) on commodity derivatives	0		0
Total sales and other operating revenues	(176)	$ (154)	(343)	$ (301)
Eliminations | Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	(176)		(343)
Eliminations | Sales of Purchased Oil and Gas
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	$ 0		$ 0