Decommissioning Trust Funds (Details 1) (USD $)	3 Months Ended	6 Months Ended	12 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Fair value of debt securities by contractual maturities
Less than 1 year	$ 51,000,000		$ 51,000,000		$ 37,000,000
1 year - 5 years	564,000,000		564,000,000		557,000,000
5 years - 10 years	548,000,000		548,000,000		512,000,000
10 years - 15 years	161,000,000		161,000,000		163,000,000
15 years - 20 years	46,000,000		46,000,000		47,000,000
20 years+	201,000,000		201,000,000		204,000,000
Total	1,571,000,000		1,571,000,000		1,520,000,000
Decommissioning Trust Funds (Textuals) [Abstract]
Amortized cost of debt securities	1,508,000,000		1,508,000,000		1,475,000,000
Average coupon rate of debt securities	4.23%		4.23%
Average duration of debt securities	5.16		5.16
Average maturity of debt securities	8.62		8.62
Proceeds from the dispositions of debt securities	144,000,000	716,000,000	636,000,000	1,487,000,000
Gains from dispositions of debt securities, gross	4,000,000	9,000,000	8,000,000	24,000,000
Losses from dispositions of debt securities, gross	1,000,000	2,000,000	6,000,000	4,000,000
Other than temporary impairment losses	0	0	0	0
Deferred taxes on unrealized gains/(losses) recorded in OCI for non-regulated decomm trusts			$ 159,000,000		$ 130,000,000

Available For Sale Securities Debt Maturities After Fifteen to twenty Years Fair Value.

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Available for sale securities debt maturities after ten to fifteen years fair value.

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Available For Sale Securities Debt Maturities After Twenty Years Fair Value.

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Average Coupon Rate Of Debt Securities Percentage.

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Average duration of debt securities.

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Average maturity of debt securities.

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Decommissioning Trust Funds Textuals Abstract.

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This item represents the fair value of debt securities which are expected to mature after five years and through ten years from the balance sheet date and which are categorized neither as held-to-maturity nor trading securities.

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-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 20
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This item represents the fair value of debt securities which are expected to mature after one year and through five years from the balance sheet date and which are categorized neither as held-to-maturity nor trading securities.

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This item represents the total of all debt securities grouped by maturity dates, at cost, net of adjustments made for accretion, amortization, other-than-temporary impairments, and hedging, if any, which are classified neither as held-to-maturity nor trading securities.

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This item represents the total of all debt securities grouped by maturity dates, at fair value, which are categorized neither as held-to-maturity nor trading securities.

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This item represents the fair value of debt securities which are expected to mature within one year of the balance sheet date and which are categorized neither as held-to-maturity nor trading securities.

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This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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This item represents the tax effects occurring during the period which are related to the net unrealized gain or loss resulting from changes in the fair [carrying] value during the period of available-for-sale securities. Such tax affects would have been charged or credited directly to other comprehensive income or to related components of shareholders' equity.

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This element represents the amount by which the carrying amount exceeds the fair value of the investment. The amount is charged to income if the decline in fair value is deemed to be other than temporary.

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The cash inflow associated with the sale of debt securities classified as available-for-sale securities.

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