Supplemental Oil and Gas Disclosures - Revenue and Direct Cost Information Relating to Company's Oil and Gas Exploration and Production Activities (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Oil and gas production revenues	$ 16,947		$ 16,810		$ 12,183
Depreciation, depletion, and amortization
Recurring	5,085	[1]	4,024	[1]	3,028	[1]
Additional	1,926		109
Asset retirement obligation accretion	232		154		111
Lease operating expenses	2,968		2,605		2,032
Gathering and transportation	303		296		178
Production taxes	817	[2]	865	[2]	656	[2]
Income tax	2,810		3,730		2,497
Oil and gas properties production expense	14,141		11,783		8,502
Results of operation	2,806		5,027		3,681
Amortization rate per boe	16.88		13.97		11.92
United States [Member]
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Oil and gas production revenues	6,226		6,103		4,300
Depreciation, depletion, and amortization
Recurring	1,984	[1]	1,634	[1]	1,126	[1]
Asset retirement obligation accretion	112		97		62
Lease operating expenses	1,386		1,167		924
Gathering and transportation	69		64		42
Production taxes	279	[2]	255	[2]	177	[2]
Income tax	851		1,025		699
Oil and gas properties production expense	4,681		4,242		3,030
Results of operation	1,545		1,861		1,270
Amortization rate per boe	17.24		15.55		13.23
Canada [Member]
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Oil and gas production revenues	1,322		1,617		1,074
Depreciation, depletion, and amortization
Recurring	580	[1]	537	[1]	287	[1]
Additional	1,883
Asset retirement obligation accretion	41		26		23
Lease operating expenses	458		470		334
Gathering and transportation	163		165		75
Production taxes	42	[2]	44	[2]	31	[2]
Income tax	(466)		95		82
Oil and gas properties production expense	2,701		1,337		832
Results of operation	(1,379)		280		242
Amortization rate per boe	11.66		10.44		8.13
Egypt [Member]
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Oil and gas production revenues	4,554		4,791		3,372
Depreciation, depletion, and amortization
Recurring	924	[1]	818	[1]	754	[1]
Lease operating expenses	410		398		298
Gathering and transportation	39		35		31
Income tax	1,527		1,699		1,099
Oil and gas properties production expense	2,900		2,950		2,182
Results of operation	1,654		1,841		1,190
Amortization rate per boe	13.81		11.63		11.05
Australia [Member]
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Oil and gas production revenues	1,575		1,734		1,459
Depreciation, depletion, and amortization
Recurring	460	[1]	435	[1]	403	[1]
Asset retirement obligation accretion	17		10		9
Lease operating expenses	215		197		185
Production taxes	11	[2]	9	[2]	11	[2]
Income tax	262		325		255
Oil and gas properties production expense	965		976		863
Results of operation	610		758		596
Amortization rate per boe	17.67		16.59		13.38
North Sea [Member]
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Oil and gas production revenues	2,751		2,091		1,606
Depreciation, depletion, and amortization
Recurring	912	[1]	405	[1]	301	[1]
Asset retirement obligation accretion	58		17		15
Lease operating expenses	315		208		168
Gathering and transportation	24		25		25
Production taxes	451	[2]	538	[2]	423	[2]
Income tax	614		557		337
Oil and gas properties production expense	2,374		1,750		1,269
Results of operation	377		341		337
Amortization rate per boe	32.65		20.21		14.42
Argentina [Member]
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Oil and gas production revenues	519		474		372
Depreciation, depletion, and amortization
Recurring	225	[1]	195	[1]	157	[1]
Asset retirement obligation accretion	4		4		2
Lease operating expenses	184		165		123
Gathering and transportation	8		7		5
Production taxes	34	[2]	19	[2]	14	[2]
Income tax	22		29		25
Oil and gas properties production expense	477		419		326
Results of operation	42		55		46
Amortization rate per boe	12.39		10.87		9.56
Other International [Member]
Depreciation, depletion, and amortization
Additional	43		109
Oil and gas properties production expense	43		109
Results of operation	$ (43)		$ (109)

[1] This amount only reflects DD&A of capitalized costs of oil and gas proved properties and, therefore, does not agree with DD&A reflected on Note 13 - Business Segment Information.

[2] This amount only reflects amounts directly related to oil and gas producing properties and, therefore, does not agree with taxes other than income reflected on Note 13 - Business Segment Information.