Segment Reporting (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Total Revenues	$ 3,424,000,000	$ 2,419,000,000
INCOME (LOSS) BEFORE INCOME TAXES	165,000,000	(5,000,000)
Total Assets	42,481,000,000		41,611,000,000
Exploration and Production
Segment Reporting Information [Line Items]
Segment Reporting Information, Revenue for Reportable Segment	1,453,000,000	1,068,000,000
Segment Reporting Information, Intersegment Revenue	0	0
Total Revenues	1,453,000,000	1,068,000,000
INCOME (LOSS) BEFORE INCOME TAXES	170,000,000	86,000,000
Total Assets	37,756,000,000		37,004,000,000
Marketing, Gathering And Compression
Segment Reporting Information [Line Items]
Segment Reporting Information, Revenue for Reportable Segment	3,529,000,000	2,392,000,000
Segment Reporting Information, Intersegment Revenue	(1,748,000,000)	(1,176,000,000)
Total Revenues	1,781,000,000	1,216,000,000
INCOME (LOSS) BEFORE INCOME TAXES	129,000,000	66,000,000
Total Assets	2,499,000,000		2,291,000,000
Oilfield Services
Segment Reporting Information [Line Items]
Segment Reporting Information, Revenue for Reportable Segment	538,000,000	447,000,000
Segment Reporting Information, Intersegment Revenue	(352,000,000)	(312,000,000)
Total Revenues	186,000,000	135,000,000
INCOME (LOSS) BEFORE INCOME TAXES	22,000,000	40,000,000
Total Assets	2,190,000,000		2,115,000,000
Other Operations
Segment Reporting Information [Line Items]
Segment Reporting Information, Revenue for Reportable Segment	10,000,000	0
Segment Reporting Information, Intersegment Revenue	(6,000,000)	0
Total Revenues	4,000,000	0
INCOME (LOSS) BEFORE INCOME TAXES	(58,000,000)	(100,000,000)
Total Assets	2,526,000,000		2,529,000,000
Intercompany Eliminations
Segment Reporting Information [Line Items]
Segment Reporting Information, Revenue for Reportable Segment	(2,106,000,000)	(1,488,000,000)
Segment Reporting Information, Intersegment Revenue	2,106,000,000	1,488,000,000
Total Revenues	0	0
INCOME (LOSS) BEFORE INCOME TAXES	(98,000,000)	(97,000,000)
Total Assets	(2,490,000,000)		(2,328,000,000)
Consolidated Entities
Segment Reporting Information [Line Items]
Segment Reporting Information, Revenue for Reportable Segment	3,424,000,000	2,419,000,000
Segment Reporting Information, Intersegment Revenue	0	0
Total Revenues	3,424,000,000	2,419,000,000
INCOME (LOSS) BEFORE INCOME TAXES	165,000,000	(5,000,000)
Total Assets	$ 42,481,000,000		$ 41,611,000,000