Environmental Matters (Accrued Liability For Asbestos Suits And Workers' Compensation Proceedings) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Site Contingency [Line Items]
Regulatory assets	$ 9,205	$ 9,501
Asbestos Suits [Member]
Site Contingency [Line Items]
Accrued liability	10	10
Regulatory assets	10	10
Workers' Compensation
Site Contingency [Line Items]
Accrued liability	95	98
Regulatory assets	$ 21	$ 23

Total costs accrued as of the balance sheet date for environmental loss contingencies.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

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

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-Name Statement of Financial Accounting Standard (FAS)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 3: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 5: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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