Segment Reporting Information by Segment (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Segment Reporting Information [Line Items]
Total Revenues	$ 2,970	$ 3,977	$ 8,778	$ 8,908
Income (loss) before income taxes	(3,231)	1,511	(1,537)	2,081
Total Assets	45,671		45,671		41,835
Exploration and Production
Segment Reporting Information [Line Items]
Segment Reporting Information, Revenue for Reportable Segment	1,437	2,402	4,622	4,688
Segment Reporting Information, Intersegment Revenue	0	0	0	0
Total Revenues	1,437	2,402	4,622	4,688
Income (loss) before income taxes	(3,073)	1,552	(1,896)	2,138
Total Assets	39,485		39,485		35,403
Marketing, Gathering And Compression
Segment Reporting Information [Line Items]
Segment Reporting Information, Revenue for Reportable Segment	2,922	2,746	7,587	7,583
Segment Reporting Information, Intersegment Revenue	(1,541)	(1,324)	(3,877)	(3,739)
Total Revenues	1,381	1,422	3,710	3,844
Income (loss) before income taxes	120	78	1,279	239
Total Assets	3,951		3,951		4,047
Oilfield Services
Segment Reporting Information [Line Items]
Segment Reporting Information, Revenue for Reportable Segment	482	343	1,434	866
Segment Reporting Information, Intersegment Revenue	(330)	(190)	(988)	(490)
Total Revenues	152	153	446	376
Income (loss) before income taxes	(2)	27	96	72
Total Assets	2,067		2,067		1,571
Other Operations
Segment Reporting Information [Line Items]
Segment Reporting Information, Revenue for Reportable Segment	0	0	0	0
Segment Reporting Information, Intersegment Revenue	0	0	0	0
Total Revenues	0	0	0	0
Income (loss) before income taxes	(152)	(56)	(654)	(131)
Total Assets	2,476		2,476		2,718
Intercompany Eliminations
Segment Reporting Information [Line Items]
Segment Reporting Information, Revenue for Reportable Segment	(1,871)	(1,514)	(4,865)	(4,229)
Segment Reporting Information, Intersegment Revenue	1,871	1,514	4,865	4,229
Total Revenues	0	0	0	0
Income (loss) before income taxes	(124)	(90)	(362)	(237)
Total Assets	(2,308)		(2,308)		(1,904)
Consolidated Entities [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information, Revenue for Reportable Segment	2,970	3,977	8,778	8,908
Segment Reporting Information, Intersegment Revenue	0	0	0	0
Total Revenues	2,970	3,977	8,778	8,908
Income (loss) before income taxes	(3,231)	1,511	(1,537)	2,081
Total Assets	$ 45,671		$ 45,671		$ 41,835