Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues	$ 651	$ 749	$ 1,752	$ 2,446
Depreciation, depletion and amortization expense	99	275	349	876
Impairment of natural gas and oil properties	817	2,839	2,321	4,374
Operating income (loss)	(725)	(2,842)	(2,317)	(3,961)
Interest expense	26		57	52
Gain (loss) on derivatives	71	15	(28)	30
Loss on early extinguishment of debt	(51)		(51)
Other income (loss), net	3			2
Provision (benefit) for income taxes	(20)	(1,088)	(20)	(1,532)
Assets	6,890	10,703	6,890	10,703	$ 8,086
Capital investments	180	468	376	2,054
Restructuring charges	2		77
Change in accrued expenditures	27	6	(24)	(5)
Gain on sale of assets, net		(1)		276
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(409)	(486)	(1,108)	(1,639)
Exploration and Production [Member]
Segment Reporting Information [Line Items]
Revenues	381	491	1,015	1,647
Depreciation, depletion and amortization expense	83	255	300	824
Impairment of natural gas and oil properties	817	2,839	2,321	4,374
Operating income (loss)	(777)	(2,910)	(2,486)	(4,471)
Interest expense	26		56	45
Gain (loss) on derivatives	71	15	(27)	32
Other income (loss), net	2		3	2
Provision (benefit) for income taxes	(20)	(1,112)	(20)	(1,724)
Assets	4,015	9,159	4,015	9,159
Capital investments	179	461	372	1,880
Restructuring charges	2		74
Exploration and Production [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	3	3	17	14
Midstream Services [Member]
Segment Reporting Information [Line Items]
Revenues	270	258	737	798
Depreciation, depletion and amortization expense	16	20	49	52
Operating income (loss)	52	68	169	511
Interest expense			1	7
Gain (loss) on derivatives			(1)
Other income (loss), net	1		(2)
Provision (benefit) for income taxes		24		193
Assets	1,253	1,329	1,253	1,329
Capital investments	1	7	3	164
Restructuring charges			3
Gain on sale of assets, net			277
Midstream Services [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(412)	(489)	(1,125)	(1,653)
Other [Member]
Segment Reporting Information [Line Items]
Revenues				1
Operating income (loss)				(1)
Gain (loss) on derivatives				(2)
Loss on early extinguishment of debt	(51)		(51)
Other income (loss), net			(1)
Provision (benefit) for income taxes				(1)
Assets	1,622	215	1,622	215
Capital investments			1	10
Marketable securities	1,443		1,443
Marketing [Member] | Midstream Services [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	$ (355)	(414)	$ (941)	(1,400)
WPX and Statoil Property Acquisitions [Member] | Exploration and Production [Member]
Segment Reporting Information [Line Items]
Capital investments		$ 516
WPX Property Acquisition [Member] | Midstream Services [Member]
Segment Reporting Information [Line Items]
Capital investments				$ 119