Segment Information - Table (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Operating Revenues	$ 1,279	$ 440	$ 2,748	$ 1,433
Revenues	2,281	1,622	5,034	3,575
Income (Loss) Before Income Taxes	496	(1,776)	638	(2,844)
TOTAL ASSETS	11,920		11,920		$ 13,028
Scenario, Previously Reported [Member]
Segment Reporting Information [Line Items]
Income (Loss) Before Income Taxes		(1,750)		(2,671)
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(1,050)	(848)	(2,170)	(1,631)
Intersegment Revenues	1,050	848	2,170	1,631
Revenues	0	0	0	0
Income (Loss) Before Income Taxes	28	57	(1)	0
TOTAL ASSETS	(411)		(411)		(398)
Intersegment Eliminations [Member] | Scenario, Previously Reported [Member]
Segment Reporting Information [Line Items]
Income (Loss) Before Income Taxes		57		0
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Operating Revenues	2,281	1,622	5,034	3,575
Intersegment Revenues	0	0	0	0
Exploration And Production [Member]
Segment Reporting Information [Line Items]
Revenues	1,279	440	2,748	1,433
Exploration And Production [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating Revenues	1,279	440	2,748	1,433
Intersegment Revenues	0	0	0	0
Income (Loss) Before Income Taxes	541	(1,781)	1,108	(2,823)
TOTAL ASSETS	10,385		10,385		11,249
Exploration And Production [Member] | Operating Segments [Member] | Scenario, Previously Reported [Member]
Segment Reporting Information [Line Items]
Income (Loss) Before Income Taxes		(1,755)		(2,650)
Marketing, Gathering And Compression [Member]
Segment Reporting Information [Line Items]
Revenues	1,002	1,182	2,286	2,142
Marketing, Gathering And Compression [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating Revenues	2,052	2,030	4,456	3,773
Intersegment Revenues	(1,050)	(848)	(2,170)	(1,631)
Income (Loss) Before Income Taxes	(61)	(44)	(447)	(4)
TOTAL ASSETS	932		932		1,118
Marketing, Gathering And Compression [Member] | Operating Segments [Member] | Scenario, Previously Reported [Member]
Segment Reporting Information [Line Items]
Income (Loss) Before Income Taxes		(44)		(4)
Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Other Segments [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating Revenues	0	0	0	0
Intersegment Revenues	0	0	0	0
Income (Loss) Before Income Taxes	(12)	(8)	(22)	(17)
TOTAL ASSETS	$ 1,014		$ 1,014		$ 1,059
Other Segments [Member] | Corporate, Non-Segment [Member] | Scenario, Previously Reported [Member]
Segment Reporting Information [Line Items]
Income (Loss) Before Income Taxes		$ (8)		$ (17)