Business Segment Information (Table 2) (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Segment Reporting Information [Line Items]
Revenue from external customers	$ 1,403	$ 1,213	$ 3,628	$ 3,632
Intersegment revenue	0	0	0	0
Operation and maintenance	366	327	994	911
Loss on deconsolidation of subsidiary (Note 15)	600		600
Ceiling test charges	152	14	152	16
Depreciation, depletion and amortization	299	239	815	699
Earnings (losses) from unconsolidated affiliates	36	28	98	167
Segment EBIT	(181)	513	830	1,913
Pipelines [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	743	680	2,130	2,072
Intersegment revenue	17	12	105	37
Operation and maintenance	213	220	614	599
Loss on deconsolidation of subsidiary (Note 15)	600		600
Ceiling test charges	0	0	0	0
Depreciation, depletion and amortization	136	111	360	327
Earnings (losses) from unconsolidated affiliates	24	28	74	157
Segment EBIT	(209)	375	718	1,299
Exploration and Production [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	481	340	944	966
Intersegment revenue	172	179	494	569
Operation and maintenance	114	87	312	275
Loss on deconsolidation of subsidiary (Note 15)	0		0
Ceiling test charges	152	14	152	16
Depreciation, depletion and amortization	157	117	437	352
Earnings (losses) from unconsolidated affiliates	(3)	(2)	(4)	(3)
Segment EBIT	183	261	402	754
Marketing [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	177	174	550	556
Intersegment revenue	(186)	(190)	(591)	(601)
Operation and maintenance	0	(3)	4	0
Loss on deconsolidation of subsidiary (Note 15)	0		0
Ceiling test charges	0	0	0	0
Depreciation, depletion and amortization	0	0	0	0
Earnings (losses) from unconsolidated affiliates	0	0	0	0
Segment EBIT	(10)	(12)	(45)	(44)
Other [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	2	19	4	38
Intersegment revenue		7	2	11
Operation and maintenance	39	23	65	37
Loss on deconsolidation of subsidiary (Note 15)	0		0
Ceiling test charges	0	0	0	0
Depreciation, depletion and amortization	6	11	18	20
Earnings (losses) from unconsolidated affiliates	15	2	28	13
Segment EBIT	(145)	(111)	(245)	(96)
Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	0	0	0	0
Intersegment revenue	(3)	(8)	(10)	(16)
Operation and maintenance	0	0	(1)	0
Loss on deconsolidation of subsidiary (Note 15)	0		0
Ceiling test charges	0	0	0	0
Depreciation, depletion and amortization	0	0	0	0
Earnings (losses) from unconsolidated affiliates	0	0	0	0
Segment EBIT	$ 0	$ 0	$ 0	$ 0