Segment Reporting - Table (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenues	$ 5,046	$ 3,424
Income (Loss) Before Income Taxes	746	165
Total Assets	42,605		41,782
Exploration and Production
Segment Reporting Information [Line Items]
Revenues	1,766	1,453
Marketing, Gathering And Compression
Segment Reporting Information [Line Items]
Revenues	3,015	1,781
Oilfield Services
Segment Reporting Information [Line Items]
Revenues	239	186
Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	26	4
Reportable Subsegments [Member]
Segment Reporting Information [Line Items]
Revenues	5,046	3,424
Income (Loss) Before Income Taxes	746	165
Total Assets	42,605		41,782
Intersubsegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	0	0
Operating Segments [Member] | Reportable Subsegments [Member] | Exploration and Production
Segment Reporting Information [Line Items]
Revenues	1,766	1,453
Income (Loss) Before Income Taxes	687	170
Total Assets	36,102		35,341
Operating Segments [Member] | Reportable Subsegments [Member] | Marketing, Gathering And Compression
Segment Reporting Information [Line Items]
Revenues	5,423	3,529
Income (Loss) Before Income Taxes	105	129
Total Assets	2,950		2,430
Operating Segments [Member] | Reportable Subsegments [Member] | Oilfield Services
Segment Reporting Information [Line Items]
Revenues	510	538
Income (Loss) Before Income Taxes	(42)	22
Total Assets	2,058		2,018
Operating Segments [Member] | Reportable Subsegments [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	26	10
Income (Loss) Before Income Taxes	60	(58)
Total Assets	5,516		5,750
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	0	0
Intersegment Eliminations [Member] | Exploration and Production
Segment Reporting Information [Line Items]
Revenues	0	0
Intersegment Eliminations [Member] | Marketing, Gathering And Compression
Segment Reporting Information [Line Items]
Revenues	(2,408)	(1,748)
Intersegment Eliminations [Member] | Oilfield Services
Segment Reporting Information [Line Items]
Revenues	(271)	(352)
Intersegment Eliminations [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	0	(6)
Intersegment Eliminations [Member] | Reportable Subsegments [Member]
Segment Reporting Information [Line Items]
Revenues	(2,679)	(2,106)
Income (Loss) Before Income Taxes	(64)	(98)
Total Assets	(4,021)		(3,757)
Intersegment Eliminations [Member] | Intersubsegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	$ 2,679	$ 2,106