Commitments And Contingencies (Third-Party Power Purchases) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Long-term Purchase Commitment [Line Items]
2013	$ 3,094
2014	3,434
2015	3,414
2016	3,298
2017	3,140
Thereafter	36,518
Total	52,898
QF Energy Payments [Member]
Long-term Purchase Commitment [Line Items]
2013	892
2014	914
2015	727
2016	618
2017	490
Thereafter	2,238
Total	5,879
Renewable (Other Than QF) Energy [Member]
Long-term Purchase Commitment [Line Items]
2013	1,356
2014	1,843
2015	2,038
2016	2,054
2017	2,053
Thereafter	30,958
Total	40,302
Other, Energy Payments [Member]
Long-term Purchase Commitment [Line Items]
2013	846
2014	677
2015	649
2016	626
2017	597
Thereafter	3,322
Total	$ 6,717

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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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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

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

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

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

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

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