Earnings Per Share (Details) (USD $) In Millions, except Per Share data	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Reconciliation of basic and diluted earnings per share of common stock
Earnings available to FirstEnergy Corp.	$ 181	$ 265	$ 231	$ 420
Weighted average number of basic shares outstanding	418	304	380	304
Assumed exercise of dilutive stock options and awards	2	1	2	1
Diluted	420	305	382	305
Basic Earnings Per Share	$ 0.43	$ 0.87	$ 0.61	$ 1.38
Diluted Earnings Per Share	$ 0.43	$ 0.87	$ 0.61	$ 1.37
Earnings Per Share (Textuals)
Number of shares issued in connection with merger of Allegheny Energy			113

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

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-Glossary Other Comprehensive Income
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+ Details

- Definition

The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

+ References+ Details

- Definition

Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

+ References

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+ Details