Revenues Revenues from Contracts with Customers by Product Type and Geographic Areas (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 5,902	$ 4,247	$ 2,996
United States E&P
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	4,886
United States E&P | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,912
United States E&P | Bakken
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,668
United States E&P | Oklahoma
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	791
United States E&P | Northern Delaware
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	293
United States E&P | Other U.S.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	222
United States E&P | Crude oil and condensate
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	3,947
United States E&P | Crude oil and condensate | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,554
United States E&P | Crude oil and condensate | Bakken
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,568
United States E&P | Crude oil and condensate | Oklahoma
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	426
United States E&P | Crude oil and condensate | Northern Delaware
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	235
United States E&P | Crude oil and condensate | Other U.S.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	164
United States E&P | Natural gas liquids
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	495
United States E&P | Natural gas liquids | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	205
United States E&P | Natural gas liquids | Bakken
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	62
United States E&P | Natural gas liquids | Oklahoma
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	181
United States E&P | Natural gas liquids | Northern Delaware
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	38
United States E&P | Natural gas liquids | Other U.S.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	9
United States E&P | Natural gas
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	413
United States E&P | Natural gas | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	145
United States E&P | Natural gas | Bakken
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	38
United States E&P | Natural gas | Oklahoma
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	184
United States E&P | Natural gas | Northern Delaware
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	20
United States E&P | Natural gas | Other U.S.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	26
United States E&P | Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	31
United States E&P | Other | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8
United States E&P | Other | Bakken
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0
United States E&P | Other | Oklahoma
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0
United States E&P | Other | Northern Delaware
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0
United States E&P | Other | Other U.S.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	23
International
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,016
International | E.G.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	384
International | U.K.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	359
International | Libya
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	196
International | Other International
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	77
International | Crude oil and condensate
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	888
International | Crude oil and condensate | E.G.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	342
International | Crude oil and condensate | U.K.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	282
International | Crude oil and condensate | Libya
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	187
International | Crude oil and condensate | Other International
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	77
International | Natural gas liquids
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	9
International | Natural gas liquids | E.G.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	4
International | Natural gas liquids | U.K.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	5
International | Natural gas liquids | Libya
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0
International | Natural gas liquids | Other International
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0
International | Natural gas
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	86
International | Natural gas | E.G.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	37
International | Natural gas | U.K.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	40
International | Natural gas | Libya
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	9
International | Natural gas | Other International
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0
International | Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	33
International | Other | E.G.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1
International | Other | U.K.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	32
International | Other | Libya
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0
International | Other | Other International
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 0