Regulatory Assets and Liabilities (Details) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Regulatory Assets
Regulatory Assets, Current	$ 469	$ 378
Regulatory asset, Long-term	4,690	4,347
Total Regulatory Assets	5,159	4,725
Regulatory Liabilities
Regulatory Liabilities, Current	820	738
Regulatory Liabilities, Long-term	4,759	4,524
Total Regulatory Liabilities	5,579	5,262
Regulatory balancing accounts, current assets
Regulatory Assets
Regulatory Assets, Current	268	213
Energy derivatives
Regulatory Assets
Regulatory Assets, Current	194	162
Regulatory asset, Long-term	465	177
Other:
Regulatory Assets
Regulatory Assets, Current	7	3
Regulatory asset, Long-term	297	280
Regulatory Liabilities
Regulatory Liabilities, Current	2	5
Deferred income taxes - net
Regulatory Assets
Regulatory asset, Long-term	1,912	1,855
Pensions and other postretirement benefits
Regulatory Assets
Regulatory asset, Long-term	1,089	1,097
Unamortized generation investment - net
Regulatory Assets
Regulatory asset, Long-term	328	355
Unamortized loss on reacquired debt
Regulatory Assets
Regulatory asset, Long-term	258	268
Nuclear-related ARO investment - net
Regulatory Assets
Regulatory asset, Long-term	163	154
Unamortized distribution investment - net
Regulatory Assets
Regulatory asset, Long-term	125	105
Regulatory balancing accounts, noncurrent assets
Regulatory Assets
Regulatory asset, Long-term	53	56
Costs of removal
Regulatory Liabilities
Regulatory Liabilities, Long-term	2,663	2,623
ARO
Regulatory Liabilities
Regulatory Liabilities, Long-term	1,250	1,099
Regulatory balancing accounts, liabilities
Regulatory Liabilities
Regulatory Liabilities, Current	818	733
Regulatory Liabilities, Long-term	$ 846	$ 802

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- Definition

The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 71
-Paragraph 9, 10

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- Definition

Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 71
-Paragraph 9, 10

+ Details

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- Definition

Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 71
-Paragraph 9, 10

+ Details

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- Definition

The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 71
-Paragraph 11

+ Details

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- Definition

The amount for the individual regulatory current liability as itemized in a table of regulatory current liabilities as of the end of the period

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 71
-Paragraph 11

+ Details

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- Definition

The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 71
-Paragraph 11

+ Details

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