Short-Term Borrowings and Bank Lines of Credit - Narrative (Details)		12 Months Ended
	Oct. 19, 2018 USD ($) agreement	Dec. 31, 2019 USD ($) agreement	Sep. 11, 2019 USD ($) agreement	Dec. 31, 2018 USD ($)
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Short-term borrowings		$ 1,000,000,000		$ 1,250,000,000
Average interest rate for borrowings		2.88%		3.07%
Maximum | Affiliates
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Term of revolving credit facility		364 days
Term Loan
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Outstanding borrowings	$ 1,750,000,000
Term Loan | Federal Funds Rate
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Spread on variable rate	0.50%
Term Loan | LIBOR
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Spread on variable rate	1.00%
Term Loan | $1.25B Term Loan
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Number of agreements | agreement	2		2
Term of revolving credit facility	364 days
Face amount of loan	$ 1,250,000,000
Term Loan | $500M Term Loan
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Term of revolving credit facility	2 years
Face amount of loan	$ 500,000,000
Term Loan | $1B Term Loan
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Face amount of loan			$ 1,000,000,000
Term Loan | $750M Term Loan
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Face amount of loan			$ 750,000,000
FET | Minimum
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Consolidated debt to total capitalization ratio (percent)		65.00%
FET | Maximum
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Consolidated debt to total capitalization ratio (percent)		75.00%
Revolving Credit Facility | Line of Credit
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Number of agreements | agreement		2
Maximum amount borrowed under revolving credit facility		$ 3,500,000,000.0
Revolving Credit Facility | Parent, the Utilities, FET and Certain Subsidiaries | Line of Credit
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Term of revolving credit facility		5 years
Revolving Credit Facility | FET | Line of Credit
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Line of Credit Facility, Remaining Borrowing Capacity		$ 1,000,000,000
Line of Credit | FE and the Utilities
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Line of Credit Facility, Remaining Borrowing Capacity		$ 4,000,000
Line of Credit | Letter of Credit
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Term of revolving credit facility		1 year
Line of Credit | Letter of Credit | FET
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Maximum amount borrowed under revolving credit facility		$ 100,000,000
Available for Issuance of Letters of Credit | Minimum
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Cross-default provision for other indebtedness		$ 100,000,000
Money Pool | Maximum
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Term of revolving credit facility		364 days
Money Pool | Regulated Companies
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Average interest rate for borrowings		2.27%
Money Pool | Unregulated Companies
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Average interest rate for borrowings		2.74%
FE | Revolving Credit Facility | Line of Credit
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Maximum amount borrowed under revolving credit facility		$ 2,500,000,000
Line of Credit Facility, Remaining Borrowing Capacity		2,496,000,000
FE | Line of Credit | Letter of Credit
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Maximum amount borrowed under revolving credit facility		250,000,000
FET Sub-limits | Revolving Credit Facility | Line of Credit
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Maximum amount borrowed under revolving credit facility		$ 1,000,000,000.0