Revenue - Summary of Revenue from Contracts with Customers on a Disaggregated Basis (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	$ 1,557	$ 1,380
Other operating revenues (a)	15	(34)
Total sales and other operating revenues	1,572	1,346
Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0
Crude Oil Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	810	768
Natural Gas Liquids Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	68	71
Natural Gas Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	231	178
Sales of Purchased Oil and Gas
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	448	363
Operating Segments | Exploration and Production
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	1,557	1,380
Other operating revenues (a)	15	(34)
Total sales and other operating revenues	1,572	1,346
Operating Segments | Exploration and Production | Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0
Operating Segments | Exploration and Production | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	1,218	1,028
Other operating revenues (a)	15	(34)
Total sales and other operating revenues	1,233	994
Operating Segments | Exploration and Production | United States | Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0
Operating Segments | Exploration and Production | Denmark
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	19	36
Other operating revenues (a)	0	0
Total sales and other operating revenues	19	36
Operating Segments | Exploration and Production | Denmark | Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0
Operating Segments | Exploration and Production | Libya
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	119	131
Other operating revenues (a)	0	0
Total sales and other operating revenues	119	131
Operating Segments | Exploration and Production | Libya | Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0
Operating Segments | Exploration and Production | Malaysia & JDA
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	201	185
Other operating revenues (a)	0	0
Total sales and other operating revenues	201	185
Operating Segments | Exploration and Production | Malaysia & JDA | Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0
Operating Segments | Exploration and Production | Crude Oil Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	810	768
Operating Segments | Exploration and Production | Crude Oil Revenue | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	682	593
Operating Segments | Exploration and Production | Crude Oil Revenue | Denmark
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	16	33
Operating Segments | Exploration and Production | Crude Oil Revenue | Libya
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	91	99
Operating Segments | Exploration and Production | Crude Oil Revenue | Malaysia & JDA
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	21	43
Operating Segments | Exploration and Production | Natural Gas Liquids Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	68	71
Operating Segments | Exploration and Production | Natural Gas Liquids Revenue | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	68	71
Operating Segments | Exploration and Production | Natural Gas Liquids Revenue | Denmark
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0
Operating Segments | Exploration and Production | Natural Gas Liquids Revenue | Libya
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0
Operating Segments | Exploration and Production | Natural Gas Liquids Revenue | Malaysia & JDA
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0
Operating Segments | Exploration and Production | Natural Gas Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	231	178
Operating Segments | Exploration and Production | Natural Gas Revenue | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	42	39
Operating Segments | Exploration and Production | Natural Gas Revenue | Denmark
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	3	3
Operating Segments | Exploration and Production | Natural Gas Revenue | Libya
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	6	8
Operating Segments | Exploration and Production | Natural Gas Revenue | Malaysia & JDA
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	180	128
Operating Segments | Exploration and Production | Sales of Purchased Oil and Gas
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	448	363
Operating Segments | Exploration and Production | Sales of Purchased Oil and Gas | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	426	325
Operating Segments | Exploration and Production | Sales of Purchased Oil and Gas | Denmark
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0
Operating Segments | Exploration and Production | Sales of Purchased Oil and Gas | Libya
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	22	24
Operating Segments | Exploration and Production | Sales of Purchased Oil and Gas | Malaysia & JDA
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	14
Operating Segments | Midstream
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	190	167
Other operating revenues (a)	0	0
Total sales and other operating revenues	190	167
Operating Segments | Midstream | Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	190	167
Operating Segments | Midstream | Crude Oil Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0
Operating Segments | Midstream | Natural Gas Liquids Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0
Operating Segments | Midstream | Natural Gas Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0
Operating Segments | Midstream | Sales of Purchased Oil and Gas
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	(190)	(167)
Other operating revenues (a)	0	0
Total sales and other operating revenues	(190)	(167)
Eliminations | Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	(190)	(167)
Eliminations | Crude Oil Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0
Eliminations | Natural Gas Liquids Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0
Eliminations | Natural Gas Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0
Eliminations | Sales of Purchased Oil and Gas
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	$ 0	$ 0