Segment Information - Table (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenues	$ 5,703	$ 4,867	$ 15,901	$ 12,965
Income (Loss) Before Income Taxes	1,129	387	2,246	1,561
Total Assets	40,518		40,518		41,782
Exploration and Production [Member]
Segment Reporting Information [Line Items]
Revenues	2,341	1,586	5,812	5,444
Marketing, Gathering And Compression [Member]
Segment Reporting Information [Line Items]
Revenues	3,362	3,032	9,543	6,871
Oilfield Services [Member]
Segment Reporting Information [Line Items]
Revenues	0	245	516	636
Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	0	4	30	14
Reportable Subsegments [Member]
Segment Reporting Information [Line Items]
Revenues	5,703	4,867	15,901	12,965
Income (Loss) Before Income Taxes	1,129	387	2,246	1,561
Total Assets	40,518		40,518		41,782
Intersubsegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Operating Segments [Member] | Reportable Subsegments [Member] | Exploration and Production [Member]
Segment Reporting Information [Line Items]
Revenues	2,341	1,586	5,812	5,444
Income (Loss) Before Income Taxes	987	430	2,089	654
Total Assets	34,876		34,876		35,341
Operating Segments [Member] | Reportable Subsegments [Member] | Marketing, Gathering And Compression [Member]
Segment Reporting Information [Line Items]
Revenues	5,512	5,034	16,289	12,553
Income (Loss) Before Income Taxes	113	128	325	395
Total Assets	2,420		2,420		2,430
Operating Segments [Member] | Reportable Subsegments [Member] | Oilfield Services [Member]
Segment Reporting Information [Line Items]
Revenues	0	551	1,060	1,677
Income (Loss) Before Income Taxes	0	(37)	(16)	(12)
Total Assets	0		0		2,018
Operating Segments [Member] | Reportable Subsegments [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	0	4	30	27
Income (Loss) Before Income Taxes	(63)	(48)	(24)	808
Total Assets	4,357		4,357		5,750
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations [Member] | Exploration and Production [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations [Member] | Marketing, Gathering And Compression [Member]
Segment Reporting Information [Line Items]
Revenues	(2,150)	(2,002)	(6,746)	(5,682)
Intersegment Eliminations [Member] | Oilfield Services [Member]
Segment Reporting Information [Line Items]
Revenues	0	(306)	(544)	(1,041)
Intersegment Eliminations [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	(13)
Intersegment Eliminations [Member] | Reportable Subsegments [Member]
Segment Reporting Information [Line Items]
Revenues	(2,150)	(2,308)	(7,290)	(6,736)
Income (Loss) Before Income Taxes	92	(86)	(128)	(284)
Total Assets	(1,135)		(1,135)		(3,757)
Intersegment Eliminations [Member] | Intersubsegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	$ 2,150	$ 2,308	$ 7,290	$ 6,736