XML 53 R41.htm IDEA: XBRL DOCUMENT
v3.21.1

Fair Value Measurements - Proceeds from the Sale of Investments (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2021 | Mar. 31, 2020
Proceeds from the sale of investments in available-for-sale securities, realized gains and losses on those sales, and interest and dividend income |  |
Sale proceeds | $ 5 | $ 13
Realized gains | 0 | 4
Realized Losses | 0 | (5)
Interest and dividend income | $ 3 | $ 5

X
- Definition Debt and Equity Securities, Realized Gain (Loss), Sales Proceeds + References No definition available. + Details
Name: | fe_DebtandEquitySecuritiesRealizedGainLossSalesProceeds
Namespace Prefix: | fe_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Debt and Equity Securities, Realized Gains + References No definition available. + Details
Name: | fe_DebtandEquitySecuritiesRealizedGains
Namespace Prefix: | fe_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Debt and Equity Securities, Realized Losses + References No definition available. + Details
Name: | fe_DebtandEquitySecuritiesRealizedLosses
Namespace Prefix: | fe_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Investment Income From Trusts + References No definition available. + Details
Name: | fe_InvestmentIncomeFromTrusts
Namespace Prefix: | fe_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration