Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2011	Mar. 31, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Income Taxes [Abstract]
Effective income tax rate (in hundredths)	20.00%		16.00%	12.00%	23.00%
Production tax credits	$ 84		$ 89	$ 163	$ 164
Deferred state tax benefit related to recent state tax law changes	64			64
Consolidated effect of reversal of valuation allowance related to certain state investment tax credits				26
Deferred income tax benefit associated with convertible investment tax credits	1		16	8	30
Cash received from a final settlement with a taxing authority	278			278
Reduction of liability for unrecognized tax benefits		248		248
Reduction of accrued net interest receivable	131			131
Liability for unrecognized tax benefits	18			18
Accrued net interest receivable	$ 8			$ 8

The net amount of decreases in accrued interest receivable resulting from settlements with taxing authorities.

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Deferred income tax benefit related to the difference between the financial statement and tax bases of renewable property.

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Deferred state tax benefit related to recent state tax law changes reflected in the Corporate and Other Segment.

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The amount of interest receivable accrued as of the date of the statement of financial position for an overpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity.

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A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
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-Publisher FASB
-Name Accounting Standards Codification
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-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
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-Paragraph 47
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A credit or adjustment for government or taxing authority authorized decrease in taxes owed as a result of meeting certain tax policy conditions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
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The amount of the additional liability or refund received or expected based on a final settlement with a taxing authority.

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

The gross amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Interpretation (FIN)
-Number 48
-Paragraph 21
-Subparagraph a
-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
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-URI http://asc.fasb.org/extlink&oid=6527854

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The gross amount of decreases in unrecognized tax benefits resulting from settlements with taxing authorities.

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-Publisher FASB
-Name FASB Interpretation (FIN)
-Number 48
-Paragraph 21
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The amount of the change in the period in the valuation allowance for a specified deferred tax asset.

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-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
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-Paragraph 26
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