Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents	$ 160,000,000	$ 295,000,000	$ 134,000,000	$ 2,048,000,000
Allowance for Doubtful Accounts	82,000,000	58,000,000
Capitalized internal costs	48,159,000,000	41,081,000,000
Impairment of operations	1,926,000,000	109,000,000
Seismic costs	15,000,000	49,000,000
Write-down of the carrying value of Oil and Gas properties	1,900,000,000
Significant portion of reserve quantity	Greater than 25 percent
Gathering, transmission and processing facilities	5,955,000,000	5,175,000,000
Accumulated depreciation	40,867,000,000	33,771,000,000
Goodwill	1,289,000,000	1,114,000,000
Impairment of goodwill	0	0	0
Accounts payable	255,000,000	207,000,000
Net cost of third party gas	27,000,000	28,000,000	33,000,000
Maximum percentage of production available to contract partners	40.00%
Additional net tax expense related to foreign currency translation gains and losses	16,000,000	(66,000,000)	111,000,000
Current tax benefit (expense) related to foreign currency translation gains and losses	(26,000,000)	(1,000,000)	(2,000,000)
Deferred tax expense (benefit) related to foreign currency translation gains and losses	(10,000,000)	(67,000,000)	109,000,000
Realized foreign currency transactions tax expense	(11,000,000)	6,000,000	57,000,000
Other foreign currency gains and losses	24,000,000	4,000,000	(39,000,000)
Benefit of tax deductions in excess of recognized compensation cost	4,000,000	32,000,000	28,000,000
Gas Gathering Transmission And Processing Facilities [Member]
Summary Of Significant Accounting Policies [Line Items]
Accumulated depreciation	1,900,000,000	1,500,000,000
Canada [Member]
Summary Of Significant Accounting Policies [Line Items]
Capitalized internal costs	5,637,000,000	7,206,000,000
Impairment of operations	1,883,000,000
Write-down of the carrying value of Oil and Gas properties	1,900,000,000
Write-down of the carrying value of Oil and Gas properties, net of tax	1,400,000,000
Write down of oil and gas property Excluding the effect of cash flow hedge Before Tax	135,000,000
Write down of oil and gas property Excluding the effect of cash flow hedge Net of Tax	101,000,000
Goodwill	103,000,000	103,000,000
United States [Member]
Summary Of Significant Accounting Policies [Line Items]
Capitalized internal costs	27,836,000,000	20,582,000,000
Goodwill	1,000,000,000	843,000,000
United States [Member] | Cordillera Energy Partners [Member]
Summary Of Significant Accounting Policies [Line Items]
Goodwill	173,000,000
Mobil North Sea Limited [Member]
Summary Of Significant Accounting Policies [Line Items]
Goodwill	84,000,000	82,000,000
Egypt [Member]
Summary Of Significant Accounting Policies [Line Items]
Capitalized internal costs	3,377,000,000	3,060,000,000
Goodwill	86,000,000	86,000,000
NEW ZEALAND [Member]
Summary Of Significant Accounting Policies [Line Items]
Impairment of operations	28,000,000
Chile [Member]
Summary Of Significant Accounting Policies [Line Items]
Impairment of operations		60,000,000
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Voting interest required for consolidation of investments	50.00%
Minimum [Member] | Gas Gathering Transmission And Processing Facilities [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives of gas gathering, transmission and processing facilities	3 years
Maximum [Member] | Gas Gathering Transmission And Processing Facilities [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives of gas gathering, transmission and processing facilities	25 years
Apache Corporation [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents		41,000,000	6,000,000	647,000,000
Capitalized internal costs	404,000,000	335,000,000	321,000,000
Goodwill	$ 173,000,000