Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Revenues:
Customer	$ 4,018	$ 3,633	$ 11,513	$ 10,969
Sales to related parties	16	16	43	45
Segment revenues, total	4,034	3,649	11,556	11,014
Segment income	590	477	1,593	1,950
Income from equity method investments,segment	122	123	260	360
Depreciation, depletion and amortization, segment	625	517	1,779	1,716
Income tax provision, segment	1,279	898	3,231	2,051
Exploration and Production Segment [Member]
Revenues:
Customer	3,503	3,190	10,284	9,696
Elimination of intersegment revenues		6		47
Sales to related parties	16	16	43	45
Segment revenues, total	3,519	3,212	10,327	9,788
Elimination of intersegment revenues		(6)		(47)
Total revenue
Segment income	486	330	1,380	1,599
Income from equity method investments,segment	74	63	176	187
Depreciation, depletion and amortization, segment	556	454	1,593	1,541
Income tax provision, segment	1,252	890	3,398	2,101
Capital expenditures, segment	1,274	684	3,459	2,101
Oil Sands Mining Segment [Member]
Revenues:
Customer	470	427	1,184	1,180
Elimination of intersegment revenues		0		0
Sales to related parties	0	0	0	0
Segment revenues, total	470	427	1,184	1,180
Elimination of intersegment revenues		0		0
Total revenue
Segment income	65	92	157	193
Income from equity method investments,segment	0	0	0	0
Depreciation, depletion and amortization, segment	60	55	159	141
Income tax provision, segment	20	31	51	64
Capital expenditures, segment	41	36	136	236
Integrated Gas Segment [Member]
Revenues:
Customer	0	16	0	93
Elimination of intersegment revenues		0		0
Sales to related parties	0	0	0	0
Segment revenues, total	0	16	0	93
Elimination of intersegment revenues		0		0
Total revenue
Segment income	39	55	56	158
Income from equity method investments,segment	48	60	84	173
Depreciation, depletion and amortization, segment	0	0	0	3
Income tax provision, segment	9	19	15	62
Capital expenditures, segment	1	1	2	2
Total All Segments [Member]
Revenues:
Customer	3,973	3,633	11,468	10,969
Elimination of intersegment revenues		6		47
Sales to related parties	16	16	43	45
Segment revenues, total	3,989	3,655	11,511	11,061
Unrealized gain on crude oil derivative instruments	45		45
Elimination of intersegment revenues		(6)		(47)
Total revenue	4,034	3,649	11,556	11,014
Segment income	590	477	1,593	1,950
Income from equity method investments,segment	122	123	260	360
Depreciation, depletion and amortization, segment	616	509	1,752	1,685
Income tax provision, segment	1,281	940	3,464	2,227
Capital expenditures, segment	$ 1,316	$ 721	$ 3,597	$ 2,339