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Change to Company's earnings resulting from retiree healthcare liabilities and related tax impact already reflected in consolidated financial statements.

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Income tax benefits on settlement of recognized research and development claim.

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Tax benefits arising from favorable affected tax rate included in research and development settlement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Reflects the effects of adjustments of previously recorded tax expense, significant settlements of income tax disputes, and unusual tax positions or infrequent actions taken by the entity, including tax assessment reversal, IRS tax settlement and unusual repatriation of foreign earnings.

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

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The gross amount of decreases in unrecognized tax benefits resulting from tax positions that have been or will be taken in the tax return for the current period, excluding amounts pertaining to examined tax returns.

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The gross amount of increases in unrecognized tax benefits resulting from tax positions that have been or will be taken in the tax return for the current period, excluding amounts pertaining to examined tax returns.

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This element represents the amount of interest expense accrued as of the date of the statement of financial position for an underpayment 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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This element represents interest expense recognized for an underpayment 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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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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Income Taxes (Details) (USD $) In Millions	3 Months Ended		6 Months Ended		9 Months Ended
Income Taxes (Details) (USD $) In Millions	Mar. 31, 2011	Mar. 31, 2010	Jun. 30, 2011	Jun. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Income Tax Contingency [Line Items]
Increase in unrecognized tax benefits	$ 97
Income tax benefits on settlement of recognized research and development claim			30
Tax benefits arising from favorable affected tax rate included in Research and development settlement			5
Decrease in unrecognized tax benefits				78
Tax benefits favorably affecting effective tax rate				21		11
Unrecognized tax benefits expected to resolved within the next twelve month					46
Unrecognized benefits (if recognized) affecting effective tax rate			6		4
Accrued Interest					11		3
Change in effective tax rate as a result of non-deductible portion of merger transaction and integration costs					28
Change to FirstEnergy's earnings resulting from retiree healthcare liabilities and related tax impact already reflected in consolidated financial statements		13
Allegheny
Income Tax Contingency [Line Items]
Increase in accrued interest					$ 6