Revenues - Revenues from Contracts with Customers by Product Type and Geographic Areas (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
United States Exploration and Production [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	$ 1,125
United States Exploration and Production [Member] | Eagle Ford [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	443
United States Exploration and Production [Member] | Bakken [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	355
United States Exploration and Production [Member] | Oklahoma [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	195
United States Exploration and Production [Member] | Northern Delaware [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	66
United States Exploration and Production [Member] | Other U.S. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	66
United States Exploration and Production [Member] | Crude oil and condensate [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	919
United States Exploration and Production [Member] | Crude oil and condensate [Member] | Eagle Ford [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	366
United States Exploration and Production [Member] | Crude oil and condensate [Member] | Bakken [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	330
United States Exploration and Production [Member] | Crude oil and condensate [Member] | Oklahoma [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	115
United States Exploration and Production [Member] | Crude oil and condensate [Member] | Northern Delaware [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	55
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	53
United States Exploration and Production [Member] | Natural gas liquids [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	103
United States Exploration and Production [Member] | Natural gas liquids [Member] | Eagle Ford [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	42
United States Exploration and Production [Member] | Natural gas liquids [Member] | Bakken [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	15
United States Exploration and Production [Member] | Natural gas liquids [Member] | Oklahoma [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	37
United States Exploration and Production [Member] | Natural gas liquids [Member] | Northern Delaware [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	6
United States Exploration and Production [Member] | Natural gas liquids [Member] | Other U.S. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	3
United States Exploration and Production [Member] | Natural gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	98
United States Exploration and Production [Member] | Natural gas [Member] | Eagle Ford [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	33
United States Exploration and Production [Member] | Natural gas [Member] | Bakken [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	10
United States Exploration and Production [Member] | Natural gas [Member] | Oklahoma [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	43
United States Exploration and Production [Member] | Natural gas [Member] | Northern Delaware [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	5
United States Exploration and Production [Member] | Natural gas [Member] | Other U.S. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	7
United States Exploration and Production [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	5
United States Exploration and Production [Member] | Other [Member] | Eagle Ford [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	2
United States Exploration and Production [Member] | Other [Member] | Bakken [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0
United States Exploration and Production [Member] | Other [Member] | Oklahoma [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0
United States Exploration and Production [Member] | Other [Member] | Northern Delaware [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0
United States Exploration and Production [Member] | Other [Member] | Other U.S. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	3
International Exploration and Production [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	412
International Exploration and Production [Member] | E.G. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	81
International Exploration and Production [Member] | U.K. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	112
International Exploration and Production [Member] | Libya [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	196
International Exploration and Production [Member] | Other International [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	23
International Exploration and Production [Member] | Crude oil and condensate [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	376
International Exploration and Production [Member] | Crude oil and condensate [Member] | E.G. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	71
International Exploration and Production [Member] | Crude oil and condensate [Member] | U.K. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	95
International Exploration and Production [Member] | Crude oil and condensate [Member] | Libya [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	187
International Exploration and Production [Member] | Crude oil and condensate [Member] | Other International [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	23
International Exploration and Production [Member] | Natural gas liquids [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	1
International Exploration and Production [Member] | Natural gas liquids [Member] | E.G. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	1
International Exploration and Production [Member] | Natural gas liquids [Member] | U.K. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0
International Exploration and Production [Member] | Natural gas liquids [Member] | Libya [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0
International Exploration and Production [Member] | Natural gas liquids [Member] | Other International [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0
International Exploration and Production [Member] | Natural gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	26
International Exploration and Production [Member] | Natural gas [Member] | E.G. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	9
International Exploration and Production [Member] | Natural gas [Member] | U.K. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	8
International Exploration and Production [Member] | Natural gas [Member] | Libya [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	9
International Exploration and Production [Member] | Natural gas [Member] | Other International [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0
International Exploration and Production [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	9
International Exploration and Production [Member] | Other [Member] | E.G. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0
International Exploration and Production [Member] | Other [Member] | U.K. [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	9
International Exploration and Production [Member] | Other [Member] | Libya [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	0
International Exploration and Production [Member] | Other [Member] | Other International [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customer	$ 0