Short-Term Borrowings and Bank Lines of Credit (Details Textuals) (USD $)	12 Months Ended			0 Months Ended	3 Months Ended
	Dec. 31, 2014 money_pool	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2014 credit_facility	Mar. 31, 2014 credit_facility	Mar. 29, 2014
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Short-term borrowings	$ 1,799,000,000	$ 3,404,000,000
Loss on debt redemptions	(8,000,000)	(132,000,000)	0
Number of money pools	2
Average interest rate for borrowings	1.96%	1.80%
Revolving Credit Facility
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Number of credit facilities extended				3	3
Revolving Credit Facility | Maximum
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Term of revolving credit facility, in days	364 days
Consolidated debt to total capitalization ratio (percent)	65.00%
Parent Company | Term Loan | Variable Rate Term Loan Due 2019
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Face amount of loan				1,000,000,000	1,000,000,000
Parent Company | Term Loan | Variable Rate Term Loan Due 2016
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Face amount of loan	200,000,000
Parent Company | Revolving Credit Facility
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Increase (decrease) in maximum borrowing capacity				1,000,000,000	1,000,000,000
Loss on debt redemptions	(5,000,000)
FES
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Maximum amount borrowed under revolving credit facility	1,500,000,000
Short-term borrowings	99,000,000	4,000,000
Loss on debt redemptions	(6,000,000)	(103,000,000)	0
Average interest rate for borrowings	3.34%	0.00%
FES | Revolving Credit Facility
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Loss on debt redemptions	(3,000,000)
FES / AE Supply | Revolving Credit Facility
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Increase (decrease) in maximum borrowing capacity				(1,000,000,000)	(1,000,000,000)
FirstEnergy
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Maximum amount borrowed under revolving credit facility	3,500,000,000
FirstEnergy | Revolving Credit Facility
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Increase (decrease) in maximum borrowing capacity				1,000,000,000	1,000,000,000
FET
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Maximum amount borrowed under revolving credit facility	1,000,000,000
FET | Revolving Credit Facility | Maximum
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Consolidated debt to total capitalization ratio (percent)	75.00%
ATSI
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Maximum amount borrowed under revolving credit facility	500,000,000
ATSI | Revolving Credit Facility
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Maximum amount borrowed under revolving credit facility				500,000,000	500,000,000	100,000,000
TrAIL
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Maximum amount borrowed under revolving credit facility	400,000,000
TrAIL | Revolving Credit Facility
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Maximum amount borrowed under revolving credit facility				400,000,000	400,000,000	200,000,000
Revolving Credit Facility | Parent and Certain Subsidiaries
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Number of credit facilities	3
Term of credit facility	5 years
Available for Issuance of Letters of Credit
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Amount of revolving line of credit	600,000,000
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
Available for Issuance of Letters of Credit | FES / AE Supply
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Amount of revolving line of credit	1,500,000,000
Available for Issuance of Letters of Credit | FET
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Amount of revolving line of credit	$ 225,000,000
Money Pool | Maximum
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Term of revolving credit facility, in days	364 days
Money Pool | Regulated Companies
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Average interest rate for borrowings	1.45%
Money Pool | Unregulated Companies
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract]
Average interest rate for borrowings	1.35%