Business Segment Information - Financial Segment Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Oil and gas production revenues	$ 4,119	$ 3,956	$ 8,265	$ 8,413
Operating Income (Loss)	1,558	988	3,117	2,643
Other Income (Expense):
Derivative instrument gains (losses), net	247		147
Other	17	16	47	95
General and administrative	(133)	(132)	(249)	(260)
Financing costs, net	(51)	(45)	(104)	(85)
INCOME BEFORE INCOME TAXES	1,638	811	2,958	2,371
Merger, acquisitions & transition		(16)		(22)
Total Assets	63,350	57,217	63,350	57,217	60,737
Operating Segments [Member] | United States [Member]
Segment Reporting Information [Line Items]
Oil and gas production revenues	1,836	1,442	3,513	2,992
Operating Income (Loss)	712	526	1,298	1,197
Other Income (Expense):
Total Assets	33,376	28,453	33,376	28,453
Operating Segments [Member] | Canada [Member]
Segment Reporting Information [Line Items]
Oil and gas production revenues	329	295	627	648
Operating Income (Loss)	14	(671)	11	(1,158)
Other Income (Expense):
Total Assets	6,927	7,932	6,927	7,932
Operating Segments [Member] | Egypt [Member]
Segment Reporting Information [Line Items]
Oil and gas production revenues	893	1,011	1,902	2,260
Operating Income (Loss)	512	672	1,170	1,599
Other Income (Expense):
Total Assets	6,951	6,916	6,951	6,916
Operating Segments [Member] | Australia [Member]
Segment Reporting Information [Line Items]
Oil and gas production revenues	291	388	588	814
Operating Income (Loss)	119	202	254	453
Other Income (Expense):
Total Assets	7,124	5,487	7,124	5,487
Operating Segments [Member] | North Sea [Member]
Segment Reporting Information [Line Items]
Oil and gas production revenues	652	694	1,392	1,436
Operating Income (Loss)	202	251	448	515
Other Income (Expense):
Total Assets	7,114	6,541	7,114	6,541
Operating Segments [Member] | Argentina [Member]
Segment Reporting Information [Line Items]
Oil and gas production revenues	118	126	243	263
Operating Income (Loss)	(1)	15	(64)	44
Other Income (Expense):
Total Assets	1,728	1,810	1,728	1,810
Operating Segments [Member] | Other International [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)		(7)		(7)
Other Income (Expense):
Total Assets	$ 130	$ 78	$ 130	$ 78