Segment Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($) segment	Mar. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments | segment	2
Revenues from contracts with customers	$ 1,537	$ 873
Net gain (loss) on commodity derivatives	(102)	81
Marketing revenues	0	34
Income from equity method investments	37	69
Net gain ( loss) on disposal of assets and other income	257	1
Other Operating Income	4	14
Oil and Gas Production Expense	217	153
Marketing costs	0	34
Other Cost and Expense, Operating	130	89
Exploration Expense	52	28
Depreciation, depletion and amortization	590	556
Impairments	8	4
Taxes other than income	64	39
General and Administrative Expense	100	97
Net interest and other	45	78
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	3	10
Income tax provision (benefit)	168	34
Segment income (loss) / Income (loss) from continuing operations	356	(50)
Capital expenditures	622	359
Pension Plan [Member]
Segment Reporting Information [Line Items]
Net settlement loss	4	14
Oil Sands Mining Segment [Member]
Segment Reporting Information [Line Items]
Impairments	0	6,636
Operating Segments [Member] | United States Exploration and Production [Member]
Segment Reporting Information [Line Items]
Revenues from contracts with customers	1,125	670
Net gain (loss) on commodity derivatives	(59)	4
Marketing revenues		6
Income from equity method investments	0	0
Net gain ( loss) on disposal of assets and other income	0	1
Other Operating Income	3	4
Oil and Gas Production Expense	151	109
Marketing costs		7
Other Cost and Expense, Operating	111	74
Exploration Expense	51	26
Depreciation, depletion and amortization	528	472
Impairments	0	4
Taxes other than income	64	39
General and Administrative Expense	36	33
Net interest and other	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0	0
Income tax provision (benefit)	3	0
Segment income (loss) / Income (loss) from continuing operations	125	(79)
Capital expenditures	611	349
Operating Segments [Member] | International Exploration and Production [Member]
Segment Reporting Information [Line Items]
Revenues from contracts with customers	412	203
Net gain (loss) on commodity derivatives	0	0
Marketing revenues		28
Income from equity method investments	37	69
Net gain ( loss) on disposal of assets and other income	0	0
Other Operating Income	1	10
Oil and Gas Production Expense	67	44
Marketing costs		27
Other Cost and Expense, Operating	19	15
Exploration Expense	1	2
Depreciation, depletion and amortization	54	75
Impairments	0	0
Taxes other than income	0	0
General and Administrative Expense	9	6
Net interest and other	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	(2)	(2)
Income tax provision (benefit)	170	50
Segment income (loss) / Income (loss) from continuing operations	132	93
Capital expenditures	6	9
Corporate, Non-Segment [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0	0
Net gain (loss) on commodity derivatives	(43)	77
Marketing revenues		0
Income from equity method investments	0	0
Net gain ( loss) on disposal of assets and other income	257	0
Other Operating Income	0	0
Oil and Gas Production Expense	(1)	0
Marketing costs		0
Other Cost and Expense, Operating	0	0
Exploration Expense	0	0
Depreciation, depletion and amortization	8	9
Impairments	8	0
Taxes other than income	0	0
General and Administrative Expense	55	58
Net interest and other	45	78
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	5	12
Income tax provision (benefit)	(5)	(16)
Segment income (loss) / Income (loss) from continuing operations	99	(64)
Capital expenditures	$ 5	$ 1