Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended				12 Months Ended		3 Months Ended			12 Months Ended					12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2011 Gas Gathering Transmission And Processing Facilities [Member] Y	Dec. 31, 2010 Gas Gathering Transmission And Processing Facilities [Member] Y	Mar. 31, 2009 United States and Canada [Member]	Dec. 31, 2011 United States [Member]	Dec. 31, 2010 United States [Member]	Dec. 31, 2009 Canada [Member]	Dec. 31, 2011 Canada [Member]	Dec. 31, 2010 Canada [Member]	Dec. 31, 2011 Egypt [Member]	Dec. 31, 2010 Egypt [Member]	Dec. 31, 2011 Chile [Member]	Dec. 31, 2011 Mobil North Sea Limited [Member]	Dec. 31, 2011 Apache Corporation [Member]	Dec. 31, 2010 Apache Corporation [Member]	Dec. 31, 2009 Apache Corporation [Member]	Dec. 31, 2008 Apache Corporation [Member]
Summary of Significant Accounting Policies (Textual) [Abstract]
Voting interest required for consolidation of investments	50.00%
Maturity of cash equivalents at time of purchase	3 months or less
Cash and cash equivalents	$ 295,000,000	$ 134,000,000	$ 2,048,000,000	$ 1,181,000,000													$ 41,000,000	$ 6,000,000	$ 647,000,000	$ 142,000,000
Allowance for Doubtful Accounts	58,000,000	48,000,000
Maximum percentage of reserve quantities in a country to be sold to recognize in income	25.00%
Discount rate of after-tax future net cash flows	10.00%	10.00%
Gathering, transmission and processing facilities	5,175,000,000	4,212,000,000
Impairment of gathering, transmission and processing facilities	0	0	0
Impairment of goodwill	0	0	0
Accounts payable	207,000,000	191,000,000
Net cost of third party gas	28,000,000	33,000,000	34,000,000
Maximum percentage of production available to contract partners	40.00%
Additional net tax expense related to foreign currency translation gains and losses	78,000,000	111,000,000	195,000,000
Current tax benefit (expense) related to foreign currency translation gains and losses	1,000,000	2,000,000	3,000,000
Deferred tax expense related to foreign currency translation gains and losses	79,000,000	109,000,000	198,000,000
Other foreign currency gains and losses	4,000,000	39,000,000	11,000,000
Realized foreign currency transactions tax expense	6,000,000	57,000,000
Benefit of tax deductions in excess of recognized compensation cost	32,000,000	28,000,000	16,000,000
Capitalized Costs Relating to Oil and Gas Producing Activities, by Geographic Area [Line Items]
Capitalized internal costs	41,081,000,000	34,622,000,000									7,206,000,000	6,765,000,000	3,060,000,000	2,857,000,000			335,000,000	321,000,000	219,000,000
Amortization Expense by Geographic Segment [Line Items]
Write-down of the carrying value of Oil and Gas properties							2,820,000,000
Write-down of the carrying value of Oil and Gas properties, net of tax							1,980,000,000
Write down of oil and gas property Excluding the effect of cash flow hedge Before Tax							3,400,000,000
Write down of oil and gas property Excluding the effect of cash flow hedge Net of Tax							2,400,000,000
Write down of oil and gas property Excluding the effect of cash flow hedge before tax											92,000,000	69,000,000
Impairment of operations	109,000,000		2,818,000,000							1,596,000,000					60,000,000
Seismic costs	49,000,000
Public Utility, Property, Plant and Equipment [Line Items]
Minimum useful lives of gas gathering, transmission and processing facilities					3
Maximum useful lives of gas gathering, transmission and processing facilities						25
Accumulated depreciation	33,771,000,000	29,595,000,000			1,500,000,000	1,300,000,000
Goodwill [Line Items]
Goodwill	$ 1,114,000,000	$ 1,032,000,000						$ 843,000,000	$ 843,000,000		$ 103,000,000	$ 103,000,000	$ 86,000,000	$ 86,000,000		$ 82,000,000	$ 0	$ 0