Revenues - Revenues from Contracts with Customers by Product Type and Geographic Areas (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 1,249	$ 1,538	$ 3,830	$ 4,522
United States E&P
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,172	1,347	3,434	3,693
United States E&P | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	388	542	1,190	1,458
United States E&P | Bakken
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	466	475	1,334	1,260
United States E&P | Oklahoma
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	181	208	503	597
United States E&P | Northern Delaware
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	96	77	259	210
United States E&P | Other U.S.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	41	45	148	168
United States E&P | Crude oil and condensate
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,017	1,090	2,897	3,022
United States E&P | Crude oil and condensate | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	336	436	1,004	1,196
United States E&P | Crude oil and condensate | Bakken
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	452	447	1,277	1,182
United States E&P | Crude oil and condensate | Oklahoma
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	116	114	304	340
United States E&P | Crude oil and condensate | Northern Delaware
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	88	59	229	173
United States E&P | Crude oil and condensate | Other U.S.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	25	34	83	131
United States E&P | Natural gas liquids
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	64	152	225	370
United States E&P | Natural gas liquids | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	23	70	88	157
United States E&P | Natural gas liquids | Bakken
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	6	19	31	51
United States E&P | Natural gas liquids | Oklahoma
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	28	48	81	130
United States E&P | Natural gas liquids | Northern Delaware
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	5	12	20	24
United States E&P | Natural gas liquids | Other U.S.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2	3	5	8
United States E&P | Natural gas
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	81	102	263	286
United States E&P | Natural gas | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	28	36	94	102
United States E&P | Natural gas | Bakken
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8	9	26	27
United States E&P | Natural gas | Oklahoma
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	37	46	118	127
United States E&P | Natural gas | Northern Delaware
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	3	6	10	13
United States E&P | Natural gas | Other U.S.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	5	5	15	17
United States E&P | Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	10	3	49	15
United States E&P | Other | Eagle Ford
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1	0	4	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	3	45	12
International E&P
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		191	396	829
International E&P | E.G.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	77	110	243	302
International E&P | U.K.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	61	134	266
International E&P | Libya
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0			196
International E&P | Other International
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	77	20	19	65
International E&P | Crude oil and condensate
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		161	341	730
International E&P | Crude oil and condensate | E.G.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	67	100	215	271
International E&P | Crude oil and condensate | U.K.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	41	107	207
International E&P | Crude oil and condensate | Libya
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0			187
International E&P | Crude oil and condensate | Other International
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	67	20	19	65
International E&P | Natural gas liquids
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		2	4	7
International E&P | Natural gas liquids | E.G.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1	1	3	3
International E&P | Natural gas liquids | U.K.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	1	1	4
International E&P | Natural gas liquids | Libya
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0			0
International E&P | Natural gas liquids | Other International
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1	0	0	0
International E&P | Natural gas
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		20	36	68
International E&P | Natural gas | E.G.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8	9	24	28
International E&P | Natural gas | U.K.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	11	12	31
International E&P | Natural gas | Libya
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0			9
International E&P | Natural gas | Other International
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8	0	0	0
International E&P | Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		8	15	24
International E&P | Other | E.G.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		0	1	0
International E&P | Other | U.K.
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers		8	14	24
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	0
Operating Segments | United States E&P
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,172	1,347	3,434	3,693
Operating Segments | International E&P
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	77	191	396	829
Not Allocated to Segments
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 0	$ 0	$ 0	$ 0