Revenues - Revenues from Contracts with Customers by Product Type and Geographic Areas (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
United States Exploration and Production [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	$ 1,221	$ 2,346
United States Exploration and Production [Member] | Eagle Ford [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	473	916
United States Exploration and Production [Member] | Bakken [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	430	785
United States Exploration and Production [Member] | Oklahoma [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	194	389
United States Exploration and Production [Member] | Northern Delaware [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	67	133
United States Exploration and Production [Member] | Other U.S. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	57	123
United States Exploration and Production [Member] | Crude oil and condensate [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	1,013	1,932
United States Exploration and Production [Member] | Crude oil and condensate [Member] | Eagle Ford [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	394	760
United States Exploration and Production [Member] | Crude oil and condensate [Member] | Bakken [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	405	735
United States Exploration and Production [Member] | Crude oil and condensate [Member] | Oklahoma [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	111	226
United States Exploration and Production [Member] | Crude oil and condensate [Member] | Northern Delaware [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	59	114
United States Exploration and Production [Member] | Crude oil and condensate [Member] | Other U.S. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	44	97
United States Exploration and Production [Member] | Natural gas liquids [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	115	218
United States Exploration and Production [Member] | Natural gas liquids [Member] | Eagle Ford [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	45	87
United States Exploration and Production [Member] | Natural gas liquids [Member] | Bakken [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	17	32
United States Exploration and Production [Member] | Natural gas liquids [Member] | Oklahoma [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	45	82
United States Exploration and Production [Member] | Natural gas liquids [Member] | Northern Delaware [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	6	12
United States Exploration and Production [Member] | Natural gas liquids [Member] | Other U.S. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	2	5
United States Exploration and Production [Member] | Natural gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	86	184
United States Exploration and Production [Member] | Natural gas [Member] | Eagle Ford [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	33	66
United States Exploration and Production [Member] | Natural gas [Member] | Bakken [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	8	18
United States Exploration and Production [Member] | Natural gas [Member] | Oklahoma [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	38	81
United States Exploration and Production [Member] | Natural gas [Member] | Northern Delaware [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	2	7
United States Exploration and Production [Member] | Natural gas [Member] | Other U.S. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	5	12
United States Exploration and Production [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	7	12
United States Exploration and Production [Member] | Other [Member] | Eagle Ford [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	1	3
United States Exploration and Production [Member] | Other [Member] | Bakken [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0	0
United States Exploration and Production [Member] | Other [Member] | Oklahoma [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0	0
United States Exploration and Production [Member] | Other [Member] | Northern Delaware [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0	0
United States Exploration and Production [Member] | Other [Member] | Other U.S. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	6	9
International Exploration and Production [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	226	638
International Exploration and Production [Member] | E.G. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	111	192
International Exploration and Production [Member] | U.K. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	93	205
International Exploration and Production [Member] | Libya [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0	196
International Exploration and Production [Member] | Other International [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	22	45
International Exploration and Production [Member] | Crude oil and condensate [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	193	569
International Exploration and Production [Member] | Crude oil and condensate [Member] | E.G. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	100	171
International Exploration and Production [Member] | Crude oil and condensate [Member] | U.K. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	71	166
International Exploration and Production [Member] | Crude oil and condensate [Member] | Libya [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0	187
International Exploration and Production [Member] | Crude oil and condensate [Member] | Other International [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	22	45
International Exploration and Production [Member] | Natural gas liquids [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	4	5
International Exploration and Production [Member] | Natural gas liquids [Member] | E.G. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	1	2
International Exploration and Production [Member] | Natural gas liquids [Member] | U.K. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	3	3
International Exploration and Production [Member] | Natural gas liquids [Member] | Libya [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0	0
International Exploration and Production [Member] | Natural gas liquids [Member] | Other International [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0	0
International Exploration and Production [Member] | Natural gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	22	48
International Exploration and Production [Member] | Natural gas [Member] | E.G. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	10	19
International Exploration and Production [Member] | Natural gas [Member] | U.K. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	12	20
International Exploration and Production [Member] | Natural gas [Member] | Libya [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0	9
International Exploration and Production [Member] | Natural gas [Member] | Other International [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0	0
International Exploration and Production [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	7	16
International Exploration and Production [Member] | Other [Member] | E.G. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0	0
International Exploration and Production [Member] | Other [Member] | U.K. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	7	16
International Exploration and Production [Member] | Other [Member] | Libya [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0	0
International Exploration and Production [Member] | Other [Member] | Other International [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	$ 0	$ 0