Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues	$ 522	$ 764	$ 1,101	$ 1,697
Depreciation, depletion and amortization expense	107	308	250	601
Impairment of natural gas and oil properties	470	1,535	1,504	1,535
Operating income (loss)	(492)	(1,284)	(1,592)	(1,119)
Interest expense	17	1	31	52
Other income (loss), net		3	(3)	2
Gain (loss) on derivatives	(85)	1	(99)	15
Provision (benefit) for income taxes	(1)	(493)		(444)
Assets	7,377	13,480	7,377	13,480	$ 8,086
Capital investments	74	415	196	1,586
Restructuring charges	11		75
Change in accrued expenditures	27	(11)	(51)	(11)
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(321)	(492)	(699)	(1,153)
Exploration and Production [Member]
Segment Reporting Information [Line Items]
Revenues	291	496	634	1,156
Depreciation, depletion and amortization expense	90	291	217	569
Impairment of natural gas and oil properties	470	1,535	1,504	1,535
Operating income (loss)	(549)	(1,639)	(1,709)	(1,561)
Interest expense	16		30	45
Other income (loss), net	3	3	1	2
Gain (loss) on derivatives	(85)	2	(98)	17
Provision (benefit) for income taxes	(1)	(630)		(612)
Assets	5,000	11,882	5,000	11,882
Capital investments	73	389	193	1,419
Restructuring charges	11		72
Exploration and Production [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	7	6	14	11
Midstream Services [Member]
Segment Reporting Information [Line Items]
Revenues	231	267	467	540
Depreciation, depletion and amortization expense	17	17	33	32
Operating income (loss)	57	355	117	443
Interest expense	1		1	7
Other income (loss), net	(2)		(3)
Gain (loss) on derivatives			(1)
Provision (benefit) for income taxes		138		169
Assets	1,227	1,352	1,227	1,352
Capital investments		19	2	157
Restructuring charges			3
Midstream Services [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(328)	(499)	(713)	(1,164)
Other [Member]
Segment Reporting Information [Line Items]
Revenues		1		1
Operating income (loss)				(1)
Interest expense		1
Other income (loss), net	(1)		(1)
Gain (loss) on derivatives		(1)		(2)
Provision (benefit) for income taxes		(1)		(1)
Assets	1,150	246	1,150	246
Capital investments	1	7	1	10
Marketable securities	986		986
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	$ (267)	(419)	$ (586)	(995)
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