Segment Information (Details) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments				2
Sales and other operating revenues	$ 1,114		$ 781	$ 3,026	$ 2,032
Marketing revenues	48		80	117	202
Total revenues	1,162		861	3,143	2,234
Income from equity method investments	63		59	183	110
Net gain ( loss) on disposal of assets and other income	27		70	57	319
Oil and Gas Production Expense	194		160	521	532
Marketing costs	49		80	121	201
Exploration Expense	294		83	352	289
Depreciation, depletion and amortization	641		522	1,789	1,583
Impairments	201		47	205	48
Other expenses	206		287	608	759
Taxes other than income	44		35	128	113
Net interest and other	35		89	199	256
Loss on early extinguishment of debt	46		0	46	0
Income tax provision (benefit)	141		(107)	216	(414)
Segment income (loss) / Income (loss) from continuing operations	(599)		(206)	(802)	(704)
Capital expenditures	554		237	1,512	757
Derivative, Gain (Loss) on Derivative, Net	22			115
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	(56)		25	64	(89)
Marketing revenues	0		0	0	0
Total revenues	(56)		25	64	(89)
Income from equity method investments	0		0	0	0
Net gain ( loss) on disposal of assets and other income	23		44	32	277
Oil and Gas Production Expense	0		0	0	0
Marketing costs	0		0	0	0
Exploration Expense	250		38	250	179
Depreciation, depletion and amortization	8		13	25	36
Impairments	201		47	201	47
Other expenses	57		184	183	403
Taxes other than income	0		0	12	1
Net interest and other	35		89	199	256
Loss on early extinguishment of debt	46			46
Income tax provision (benefit)	35		(96)	14	(236)
Segment income (loss) / Income (loss) from continuing operations	(665)		(206)	(834)	(498)
Capital expenditures	9		3	20	11
Loss on Contract Termination			113		113
Severance Costs					8
International Exploration and Production [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	364		152	787	407
Marketing revenues	36		36	92	74
Total revenues	400		188	879	481
Income from equity method investments	63		59	183	110
Net gain ( loss) on disposal of assets and other income	0		7	14	20
Oil and Gas Production Expense	73		47	173	156
Marketing costs	35		35	91	72
Exploration Expense	3		10	5	20
Depreciation, depletion and amortization	102		66	266	184
Impairments	0		0	0	0
Other expenses	40		18	83	56
Taxes other than income	0		0	0	0
Net interest and other	0		0	0	0
Loss on early extinguishment of debt	0			0
Income tax provision (benefit)	106		19	202	5
Segment income (loss) / Income (loss) from continuing operations	104		59	256	118
Capital expenditures	4		18	27	62
North America Exploration and Production [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	806		604	2,175	1,714
Marketing revenues	12		44	25	128
Total revenues	818		648	2,200	1,842
Income from equity method investments	0		0	0	0
Net gain ( loss) on disposal of assets and other income	4		19	11	22
Oil and Gas Production Expense	121		113	348	376
Marketing costs	14		45	30	129
Exploration Expense	41		35	97	90
Depreciation, depletion and amortization	531		443	1,498	1,363
Impairments	0		0	4	1
Other expenses	109		85	342	300
Taxes other than income	44		35	116	112
Net interest and other	0		0	0	0
Loss on early extinguishment of debt	0			0
Income tax provision (benefit)	0		(30)	0	(183)
Segment income (loss) / Income (loss) from continuing operations	(38)		(59)	(224)	(324)
Capital expenditures	541		216	1,465	684
Pension Plan [Member]
Segment Reporting Information [Line Items]
Net settlement loss	8		14	25	93
Oil Sands Mining Segment [Member]
Segment Reporting Information [Line Items]
Impairments	0	$ 6,600	$ 0	6,636	$ 0
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member] | Net Interest and Other [Member]
Segment Reporting Information [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 47			$ 47