Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues	$ 764	$ 1,035	$ 1,697	$ 2,148
Operating income (loss)	(1,284)	367	(1,119)	802
Other income, net	3		2	1
Gain (loss) on derivatives	1	(8)	15	(108)
Depreciation, depletion and amortization	308	230	601	$ 455
Impairment of natural gas and oil properties	1,535		1,535
Interest expense	1	12	52	$ 25
Provision (benefit) for income taxes	(493)	140	(444)	269
Assets	13,504	8,887	13,504	8,887	$ 14,925
Capital investments	415	721	1,586	1,263
Change in accrued expenditures	(11)	56	(11)	61
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(492)	(821)	(1,153)	(1,740)
Exploration and Production [Member]
Segment Reporting Information [Line Items]
Revenues	496	721	1,156	1,517
Operating income (loss)	(1,639)	275	(1,561)	627
Other income, net	3		2	1
Gain (loss) on derivatives	2	(7)	17	(107)
Depreciation, depletion and amortization	291	216	569	427
Impairment of natural gas and oil properties	1,535		1,535
Interest expense		10	45	18
Provision (benefit) for income taxes	(630)	105	(612)	202
Assets	11,882	7,127	11,882	7,127
Capital investments	389	676	1,419	1,175
Exploration and Production [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	6	(4)	11	(10)
Exploration and Production [Member] | Canada [Member]
Segment Reporting Information [Line Items]
Assets	74	85	74	85
Midstream Services [Member]
Segment Reporting Information [Line Items]
Revenues	267	314	540	631
Operating income (loss)	355	93	443	175
Gain (loss) on derivatives		(1)		(1)
Depreciation, depletion and amortization	17	14	32	28
Interest expense		2	7	7
Provision (benefit) for income taxes	138	35	169	67
Assets	1,352	1,532	1,352	1,532
Capital investments	19	36	157	75
Midstream Services [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(499)	(817)	(1,164)	(1,730)
Other [Member]
Segment Reporting Information [Line Items]
Revenues	1		1
Operating income (loss)		(1)	(1)
Gain (loss) on derivatives	(1)		(2)
Interest expense	1
Provision (benefit) for income taxes	(1)		(1)
Assets	270	228	270	228
Capital investments	7	9	10	13
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	(419)	$ (725)	(995)	$ (1,500)
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