Revenues - Revenues from Contracts with Customers by Product Type and Geographic Areas (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 1,200	$ 1,537
United States E&P
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,062	1,125
United States E&P | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	389	443
United States E&P | Bakken
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	394	355
United States E&P | Oklahoma
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	144	195
United States E&P | Northern Delaware
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	78	66
United States E&P | Other U.S.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	57	66
United States E&P | Crude oil and condensate
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	859	919
United States E&P | Crude oil and condensate | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	318	366
United States E&P | Crude oil and condensate | Bakken
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	372	330
United States E&P | Crude oil and condensate | Oklahoma
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	77	115
United States E&P | Crude oil and condensate | Northern Delaware
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	64	55
United States E&P | Crude oil and condensate | Other U.S.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	28	53
United States E&P | Natural gas liquids
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	77	103
United States E&P | Natural gas liquids | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	35	42
United States E&P | Natural gas liquids | Bakken
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	10	15
United States E&P | Natural gas liquids | Oklahoma
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	22	37
United States E&P | Natural gas liquids | Northern Delaware
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8	6
United States E&P | Natural gas liquids | Other U.S.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2	3
United States E&P | Natural gas
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	103	98
United States E&P | Natural gas | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	34	33
United States E&P | Natural gas | Bakken
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	12	10
United States E&P | Natural gas | Oklahoma
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	45	43
United States E&P | Natural gas | Northern Delaware
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	6	5
United States E&P | Natural gas | Other U.S.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	6	7
United States E&P | Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	23	5
United States E&P | Other | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2	2
United States E&P | Other | Bakken
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
United States E&P | Other | Oklahoma
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
United States E&P | Other | Northern Delaware
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
United States E&P | Other | Other U.S.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	21	3
International E&P
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	138	412
International E&P | E.G.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	55	81
International E&P | U.K.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	73	112
International E&P | Libya
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		196
International E&P | Other International
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	10	23
International E&P | Crude oil and condensate
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	113	376
International E&P | Crude oil and condensate | E.G.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	47	71
International E&P | Crude oil and condensate | U.K.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	56	95
International E&P | Crude oil and condensate | Libya
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		187
International E&P | Crude oil and condensate | Other International
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	10	23
International E&P | Natural gas liquids
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2	1
International E&P | Natural gas liquids | E.G.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1	1
International E&P | Natural gas liquids | U.K.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1	0
International E&P | Natural gas liquids | Libya
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		0
International E&P | Natural gas liquids | Other International
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	15	26
International E&P | Natural gas | E.G.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	7	9
International E&P | Natural gas | U.K.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8	8
International E&P | Natural gas | Libya
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		9
International E&P | Natural gas | Other International
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	8	9
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	8	9
International E&P | Other | Libya
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		0
International E&P | Other | Other International
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 0	$ 0