Fair Value Measurements (Details 1) (USD $) In Millions	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Fair Value Measurements Using Significant Unobservable Inputs
Beginning balance	$ 1	$ 14	$ 1	$ 2
Realized and unrealized gains (losses):
Included in income (loss) from continuing operations	4	7	6	6
Included in other comprehensive income (loss)	0	(14)	(1)	1
Settlements	(4)	(6)	(6)	(8)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	1	0
Ending balance	1	1	1	1
Unrealized gains (losses) included in income (loss) from continuing operations relating to instruments still held at September 30	$ 1	$ 1	$ 1	$ 1

This item represents the amount of the total realized and unrealized gains or losses for the period which are included in the statement of income (or changes in net assets); the fair value of which assets and liabilities was or is measured on a recurring basis using significant unobservable inputs (Level 3).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258

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- Definition

This element represents total gains (losses) for the period (realized and unrealized), arising from assets and liabilities measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in other comprehensive income (a separate component of shareholders' equity).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Section 50

-Paragraph 2

-Subparagraph (c)(1)

-SubTopic 10

-Topic 820

-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258

+ Details

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- Definition

This element represents an asset measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258

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- Definition

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Settlements; Similar UGT element is for either 'assets' or 'liabilities' but we report our figures as net.

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- Definition

Realized and unrealized gains losses abstract; No suitable match found in UGT.

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- Definition

Transfers into Level 3 for net assets/liabilities; similar UGT element is for either 'assets' or 'liabilities'.

+ Details

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Balance Type:	debit
Period Type:	duration

- Definition

Transfers out of Level 3 for net assets/liabilities; similar UGT element is for either 'assets' or 'liabilities'.

+ Details

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Namespace Prefix:	wmb
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Unrealized gains Losses Included In Income Loss From Continuing Operations Relating To Instruments Held At Period End; no suitable UGT element is found.

+ Details

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Data Type:	xbrli:monetaryItemType
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