Business Segment Information - Financial Segment Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Oil and gas production revenues	$ 4,146	$ 4,457
Operating Income (Loss)	1,559	1,655
Other Income (Expense):
Other	(70)	79
General and administrative	(116)	(128)
Financing costs, net	(53)	(40)
Merger, acquisitions & transition		(6)
INCOME BEFORE INCOME TAXES	1,320	1,560
Total Assets	61,792	53,237	60,737
United States [Member]
Segment Reporting Information [Line Items]
Oil and gas production revenues	1,677	1,550
Operating Income (Loss)	585	672
Other Income (Expense):
Total Assets	32,205	24,209
Canada [Member]
Segment Reporting Information [Line Items]
Oil and gas production revenues	297	353
Operating Income (Loss)	(5)	(487)
Other Income (Expense):
Total Assets	6,935	8,372
Egypt [Member]
Segment Reporting Information [Line Items]
Oil and gas production revenues	1,009	1,249
Operating Income (Loss)	658	928
Other Income (Expense):
Total Assets	7,031	6,870
Australia [Member]
Segment Reporting Information [Line Items]
Oil and gas production revenues	298	426
Operating Income (Loss)	138	250
Other Income (Expense):
Total Assets	6,729	5,334
North Sea [Member]
Segment Reporting Information [Line Items]
Oil and gas production revenues	740	742
Operating Income (Loss)	246	264
Other Income (Expense):
Total Assets	7,053	6,591
Argentina [Member]
Segment Reporting Information [Line Items]
Oil and gas production revenues	125	137
Operating Income (Loss)	(63)	28
Other Income (Expense):
Total Assets	1,729	1,773
Other International [Member]
Other Income (Expense):
Total Assets	$ 110	$ 88