Fair Value Measurements (Details 3) (USD $) In Millions, unless otherwise specified
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Dec. 31, 2014
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Dec. 31, 2013
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Debt Securities |
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Amortized cost basis, unrealized gains and losses and fair values of investments in available-for-sale securities |
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Cost Basis |
$ 1,724us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember |
$ 1,881us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember |
Unrealized Gains |
27us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember |
33us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember |
Fair Value |
1,751us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember |
1,914us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember |
Equity securities |
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Amortized cost basis, unrealized gains and losses and fair values of investments in available-for-sale securities |
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Cost Basis |
533us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember |
308us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember |
Unrealized Gains |
58us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember |
9us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember |
Fair Value |
591us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember |
317us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember |
FES | Debt Securities |
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Amortized cost basis, unrealized gains and losses and fair values of investments in available-for-sale securities |
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Cost Basis |
788us-gaap_AvailableForSaleSecuritiesAmortizedCost / dei_LegalEntityAxis = fe_FesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember |
918us-gaap_AvailableForSaleSecuritiesAmortizedCost / dei_LegalEntityAxis = fe_FesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember |
Unrealized Gains |
13us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / dei_LegalEntityAxis = fe_FesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember |
17us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / dei_LegalEntityAxis = fe_FesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember |
Fair Value |
801us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = fe_FesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember |
935us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = fe_FesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember |
FES | Equity securities |
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Amortized cost basis, unrealized gains and losses and fair values of investments in available-for-sale securities |
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Cost Basis |
329us-gaap_AvailableForSaleSecuritiesAmortizedCost / dei_LegalEntityAxis = fe_FesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember |
207us-gaap_AvailableForSaleSecuritiesAmortizedCost / dei_LegalEntityAxis = fe_FesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember |
Unrealized Gains |
31us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / dei_LegalEntityAxis = fe_FesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember |
0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / dei_LegalEntityAxis = fe_FesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember |
Fair Value |
$ 360us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = fe_FesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember |
$ 207us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = fe_FesMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember |