Revenues - Revenues from Contracts with Customers by Product Type and Geographic Areas (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 490	$ 1,381	$ 1,514	$ 2,581
United States E&P
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	462	1,200	1,432	2,262
United States E&P | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	179	413	527	802
United States E&P | Bakken
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	155	474	503	868
United States E&P | Oklahoma
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	69	178	203	322
United States E&P | Northern Delaware
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	41	85	121	163
United States E&P | Other U.S.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	18	50	78	107
United States E&P | Crude oil and condensate
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	361	1,021	1,189	1,880
United States E&P | Crude oil and condensate | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	142	350	449	668
United States E&P | Crude oil and condensate | Bakken
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	147	453	477	825
United States E&P | Crude oil and condensate | Oklahoma
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	32	111	116	188
United States E&P | Crude oil and condensate | Northern Delaware
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	33	77	107	141
United States E&P | Crude oil and condensate | Other U.S.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	7	30	40	58
United States E&P | Natural gas liquids
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	37	84	88	161
United States E&P | Natural gas liquids | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	16	30	31	65
United States E&P | Natural gas liquids | Bakken
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	3	15	13	25
United States E&P | Natural gas liquids | Oklahoma
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	13	31	34	53
United States E&P | Natural gas liquids | Northern Delaware
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	4	7	7	15
United States E&P | Natural gas liquids | Other U.S.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1	1	3	3
United States E&P | Natural gas
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	54	79	121	182
United States E&P | Natural gas | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	20	32	44	66
United States E&P | Natural gas | Bakken
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	5	6	13	18
United States E&P | Natural gas | Oklahoma
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	24	36	53	81
United States E&P | Natural gas | Northern Delaware
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	4	1	7	7
United States E&P | Natural gas | Other U.S.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1	4	4	10
United States E&P | Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	10	16	34	39
United States E&P | Other | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1	1	3	3
United States E&P | Other | Bakken
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0	0
United States E&P | Other | Oklahoma
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0	0
United States E&P | Other | Northern Delaware
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0	0
United States E&P | Other | Other U.S.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	9	15	31	36
International E&P
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		181		319
International E&P | E.G.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	28	111	82	166
International E&P | U.K.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		61		134
International E&P | Other Int’l
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		9		19
International E&P | Crude oil and condensate
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		161		274
International E&P | Crude oil and condensate | E.G.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	20	101	65	148
International E&P | Crude oil and condensate | U.K.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		51		107
International E&P | Crude oil and condensate | Other Int’l
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		9		19
International E&P | Natural gas liquids
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		1		3
International E&P | Natural gas liquids | E.G.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1	1	2	2
International E&P | Natural gas liquids | U.K.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		0		1
International E&P | Natural gas liquids | Other Int’l
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		0		0
International E&P | Natural gas
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		13		28
International E&P | Natural gas | E.G.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 7	9	$ 15	16
International E&P | Natural gas | U.K.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		4		12
International E&P | Natural gas | Other Int’l
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		0		0
International E&P | Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		6		14
International E&P | Other | E.G.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		0		0
International E&P | Other | U.K.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		6		14
International E&P | Other | Other Int’l
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		$ 0		$ 0