Revenue - Summary of Revenue from Contracts with Customers on a Disaggregated Basis (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	$ 1,578	$ 1,841	$ 4,806	$ 4,802
Other operating revenues (a)	2	(48)	6	(129)
Total sales and other operating revenues	1,580	1,793	4,812	4,673
Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0	0	0
Crude Oil Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	924	1,017	2,701	2,634
Natural Gas Liquids Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	46	90	162	236
Natural Gas Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	201	230	627	619
Sales of Purchased Oil and Gas
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	407	504	1,316	1,313
Operating Segments | Exploration and Production
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	1,578	1,841	4,806	4,802
Other operating revenues (a)	2	(48)	6	(129)
Total sales and other operating revenues	1,580	1,793	4,812	4,673
Operating Segments | Exploration and Production | Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0	0	0
Operating Segments | Exploration and Production | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	1,210	1,442	3,710	3,698
Other operating revenues (a)	2	(48)	6	(129)
Total sales and other operating revenues	1,212	1,394	3,716	3,569
Operating Segments | Exploration and Production | United States | Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0	0	0
Operating Segments | Exploration and Production | Denmark
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	33	57	105	114
Other operating revenues (a)	0	0	0	0
Total sales and other operating revenues	33	57	105	114
Operating Segments | Exploration and Production | Denmark | Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0	0	0
Operating Segments | Exploration and Production | Libya
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	150	135	427	405
Other operating revenues (a)	0	0	0	0
Total sales and other operating revenues	150	135	427	405
Operating Segments | Exploration and Production | Libya | Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0	0	0
Operating Segments | Exploration and Production | Malaysia & JDA
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	185	207	564	585
Other operating revenues (a)	0	0	0	0
Total sales and other operating revenues	185	207	564	585
Operating Segments | Exploration and Production | Malaysia & JDA | Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0	0	0
Operating Segments | Exploration and Production | Crude Oil Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	924	1,017	2,701	2,634
Operating Segments | Exploration and Production | Crude Oil Revenue | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	749	826	2,193	2,111
Operating Segments | Exploration and Production | Crude Oil Revenue | Denmark
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	31	54	98	106
Operating Segments | Exploration and Production | Crude Oil Revenue | Libya
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	122	108	343	317
Operating Segments | Exploration and Production | Crude Oil Revenue | Malaysia & JDA
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	22	29	67	100
Operating Segments | Exploration and Production | Natural Gas Liquids Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	46	90	162	236
Operating Segments | Exploration and Production | Natural Gas Liquids Revenue | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	46	90	162	236
Operating Segments | Exploration and Production | Natural Gas Liquids Revenue | Denmark
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0	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	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	0	0
Operating Segments | Exploration and Production | Natural Gas Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	201	230	627	619
Operating Segments | Exploration and Production | Natural Gas Revenue | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	34	44	109	120
Operating Segments | Exploration and Production | Natural Gas Revenue | Denmark
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	2	3	7	8
Operating Segments | Exploration and Production | Natural Gas Revenue | Libya
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	5	5	17	20
Operating Segments | Exploration and Production | Natural Gas Revenue | Malaysia & JDA
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	160	178	494	471
Operating Segments | Exploration and Production | Sales of Purchased Oil and Gas
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	407	504	1,316	1,313
Operating Segments | Exploration and Production | Sales of Purchased Oil and Gas | United States
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	381	482	1,246	1,231
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	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	23	22	67	68
Operating Segments | Exploration and Production | Sales of Purchased Oil and Gas | Malaysia & JDA
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	3	0	3	14
Operating Segments | Midstream
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	215	184	595	527
Other operating revenues (a)	0	0	0	0
Total sales and other operating revenues	215	184	595	527
Operating Segments | Midstream | Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	215	184	595	527
Operating Segments | Midstream | Crude Oil Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0	0	0
Operating Segments | Midstream | Natural Gas Liquids Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0	0	0
Operating Segments | Midstream | Natural Gas Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0	0	0
Operating Segments | Midstream | Sales of Purchased Oil and Gas
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0	0	0
Eliminations
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	(215)	(184)	(595)	(527)
Other operating revenues (a)	0	0	0	0
Total sales and other operating revenues	(215)	(184)	(595)	(527)
Eliminations | Intercompany Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	(215)	(184)	(595)	(527)
Eliminations | Crude Oil Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0	0	0
Eliminations | Natural Gas Liquids Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0	0	0
Eliminations | Natural Gas Revenue
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	0	0	0	0
Eliminations | Sales of Purchased Oil and Gas
Disaggregation Of Revenue [Line Items]
Total revenues from contracts with customers	$ 0	$ 0	$ 0	$ 0