Segment Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues	$ 846	$ 579
Depreciation, depletion and amortization expense	106	143
Impairment of natural gas and oil properties		1,034
Operating income (loss)	266	(1,100)
Interest expense	32	14
Gain (loss) on derivatives	116	(14)
Loss on Early Extinguishment of Debt	(1)
Other income (loss), net	2	(3)
Provision for income taxes		1
Assets	7,196	8,518	$ 7,076
Capital investments	290	122
Restructuring charges		64
Cash and cash equivalents	1,382	1,597	$ 1,423	$ 15
Change in accrued expenditures	(52)	(78)
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(575)	(378)
Exploration and Production [Member]
Segment Reporting Information [Line Items]
Revenues	566	343
Depreciation, depletion and amortization expense	90	127
Impairment of natural gas and oil properties		1,034
Operating income (loss)	225	(1,160)
Interest expense	32	14
Gain (loss) on derivatives	116	(13)
Other income (loss), net	2	(2)
Provision for income taxes		1
Assets	4,413	5,538
Capital investments	283	120
Restructuring charges		61
Exploration and Production [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	3	7
Midstream Services [Member]
Segment Reporting Information [Line Items]
Revenues	280	236
Depreciation, depletion and amortization expense	16	16
Operating income (loss)	41	60
Gain (loss) on derivatives		(1)
Other income (loss), net		(1)
Assets	1,268	1,220
Capital investments	6	2
Restructuring charges		3
Midstream Services [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(578)	(385)
Other [Member]
Segment Reporting Information [Line Items]
Loss on Early Extinguishment of Debt	(1)
Assets	1,515	1,760
Capital investments	1
Cash and cash equivalents	1,400	1,600
Marketing [Member] | Midstream Services [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	$ (524)	$ (319)