Commitments And Contingencies (Nuclear Fuel Agreements) (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2012 Year	Sep. 30, 2011
Long-term Purchase Commitment [Line Items]
2012	$ 608
2013	3,075
2014	3,405
2015	3,418
2016	3,287
Thereafter	39,341
Total	53,134
Nuclear Fuel Agreements [Member]
Long-term Purchase Commitment [Line Items]
2012	7
2013	84
2014	127
2015	192
2016	147
Thereafter	1,022
Total	1,579
Pacific Gas And Electric Company [Member]
Long-term Purchase Commitment [Line Items]
Length of contract terms, minimum (in years)	1
Length of contract terms, maximum (in years)	14
Percentage coverage of reactor requirements through 2016	100.00%
Percentage coverage of reactor requirements through 2017	100.00%
Payments for nuclear fuel	$ 79	$ 55

Specifies the maximum contractual time period covered by the arrangement.

No definition available.

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- Definition

Specifies the minimum contractual time period covered by the arrangement.

+ References

No definition available.

+ Details

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- Definition

Percentage coverage of reactor requirements through 2016

+ References

No definition available.

+ Details

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- Definition

Percentage coverage of reactor requirements through 2017

+ References

No definition available.

+ Details

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- Details

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- Definition

Cash outflow associated with the purchase of any material that is commonly used in the generation of nuclear energy.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of the recorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 440

-SubTopic 10

-Section 50

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25383-109308

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 47

-Paragraph 10

-Subparagraph b

-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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 47

-Paragraph 6

-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.

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Amount of the recorded unconditional purchase obligation maturing after the fifth fiscal year following the latest fiscal year.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of the recorded unconditional purchase obligation maturing in the fifth fiscal year following the latest fiscal year.

+ References

+ Details

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- Definition

Amount of the recorded unconditional purchase obligation maturing in the fourth fiscal year following the latest fiscal year.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of the recorded unconditional purchase obligation maturing in the second fiscal year following the latest fiscal year.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Amount of the recorded unconditional purchase obligation maturing in the third fiscal year following the latest fiscal year.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of the recorded unconditional purchase obligation maturing in the next fiscal year following the latest fiscal year.

+ References

+ Details

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Namespace Prefix:	us-gaap_
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