Loss recognized during the period that results from the write-down of goodwill after comparing the implied fair value of reporting unit goodwill with the carrying amount of that goodwill. Goodwill is assessed at least annually for impairment.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 142
-Paragraph 45
-Subparagraph e(2)

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 142
-Paragraph 43

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 142
-Paragraph 47
-Subparagraph b

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 142
-Paragraph 20

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The charge against earnings resulting from the write down of long lived assets other than goodwill due to the difference between the carrying value and lower fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 28

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Impairment related to a cost-based investment.

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Impairments for discontinued operations.

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Fair Value Measurements (Details 2) (USD $) In Millions	12 Months Ended			3 Months Ended	9 Months Ended	12 Months Ended
Fair Value Measurements (Details 2) (USD $) In Millions	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Sep. 30, 2010 Exploration & Production [Member]	Sep. 30, 2010 Exploration & Production [Member]	Dec. 31, 2010 Exploration & Production [Member]	Dec. 31, 2009 Exploration & Production [Member]	Dec. 31, 2010 Williams Partners [Member]	Dec. 31, 2009 Others [Member]
Impairment Of Assets Measured At Fair Value On Non Recurring Basis [Line Items]
Goodwill - Exploration & Production (see Note 4)	$ 1,000				$ 1,000	$ 1,003
Producing properties and acquired unproved reserves - Exploration & Production (see Note 4)				678		678	15
Certain gathering assets- Williams Partners (see Note 4)								9
Venezuelan property - Discontinued Operations (see Note 2)	(1)	(216)	(135)
Investment in Accroven - Other (see Note 3)									75
Cost-based investment - Exploration & Production (see Note 3)							11
Total Impairments	$ 1,690	$ 312