Segment Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues	$ 579	$ 933
Depreciation, depletion and amortization expense	143	$ 293
Impairment of natural gas and oil properties	1,034
Operating income (loss)	(1,100)	$ 165
Interest expense	14	51
Other loss, net	(3)	(1)
Gain (loss) on derivatives	(14)	14
Provision for income taxes	1	49
Assets	8,518	15,561	$ 8,086
Capital investments	122	1,171
Restructuring charges	64
Marketable securities	1,550
Change in accrued expenditures	(78)
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(378)	(661)
Exploration and Production [Member]
Segment Reporting Information [Line Items]
Revenues	343	660
Depreciation, depletion and amortization expense	127	278
Impairment of natural gas and oil properties	1,034
Operating income (loss)	(1,160)	78
Interest expense	14	45
Other loss, net	(2)	(1)
Gain (loss) on derivatives	(13)	15
Provision for income taxes	1	18
Assets	5,538	13,703
Capital investments	120	1,030
Restructuring charges	61
Exploration and Production [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	7	5
Exploration and Production [Member] | Canada [Member]
Segment Reporting Information [Line Items]
Assets	53	71
Capital investments	1	1
Midstream Services [Member]
Segment Reporting Information [Line Items]
Revenues	236	273
Depreciation, depletion and amortization expense	16	15
Operating income (loss)	60	88
Interest expense		7
Other loss, net	(1)
Gain (loss) on derivatives	(1)
Provision for income taxes		31
Assets	1,220	1,616
Capital investments	2	138
Restructuring charges	3
Midstream Services [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(385)	(665)
Other [Member]
Segment Reporting Information [Line Items]
Operating income (loss)		(1)
Interest expense		(1)
Gain (loss) on derivatives		(1)
Assets	1,760	242
Capital investments		3
Other [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		(1)
Marketing [Member] | Midstream Services [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	$ (319)	(576)
WPX and Statoil Property Acquisitions [Member] | Exploration and Production [Member]
Segment Reporting Information [Line Items]
Capital investments		534
WPX Property Acquisition [Member] | Midstream Services [Member]
Segment Reporting Information [Line Items]
Capital investments		$ 119