Capitalization (Details 1) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of Capitalization [Line Items]
Secured notes	$ 5,455	$ 5,633
Unsecured debt	16,820	14,258
Capital lease obligations	91	104
Unamortized debt premiums (discounts)	(42)	(25)
Unamortized debt issuance costs	(113)	(87)
Unamortized fair value adjustments	(14)	(6)
Currently payable long-term debt	(1,082)	(1,685)
Total long-term debt and other long-term obligations	21,115	18,192
FES
Schedule of Capitalization [Line Items]
Secured notes	621	627
Capital lease obligations	2	8
Unamortized debt premiums (discounts)	(1)	(1)
Unamortized debt issuance costs	(14)	(15)
Currently payable long-term debt	(524)	(179)
Total long-term debt and other long-term obligations	2,299	2,813
FMBs and secured notes - fixed rate
Schedule of Capitalization [Line Items]
FMBs and secured notes - fixed rate	$ 5,446	5,623
FMBs and secured notes - fixed rate | Minimum
Schedule of Capitalization [Line Items]
Interest rate (percent)	1.726%
FMBs and secured notes - fixed rate | Maximum
Schedule of Capitalization [Line Items]
Interest rate (percent)	9.74%
Secured notes - fixed rate | FES
Schedule of Capitalization [Line Items]
Secured notes	$ 612	617
Secured notes - fixed rate | FES | Minimum
Schedule of Capitalization [Line Items]
Interest rate (percent)	4.25%
Secured notes - fixed rate | FES | Maximum
Schedule of Capitalization [Line Items]
Interest rate (percent)	5.625%
Secured notes - variable rate
Schedule of Capitalization [Line Items]
Secured notes	$ 9	10
Secured notes - variable rate | Minimum
Schedule of Capitalization [Line Items]
Interest rate (percent)	4.50%
Secured notes - variable rate | Maximum
Schedule of Capitalization [Line Items]
Interest rate (percent)	4.50%
Secured notes - variable rate | FES
Schedule of Capitalization [Line Items]
Secured notes	$ 9	10
Secured notes - variable rate | FES | Minimum
Schedule of Capitalization [Line Items]
Interest rate (percent)	4.50%
Secured notes - variable rate | FES | Maximum
Schedule of Capitalization [Line Items]
Interest rate (percent)	4.50%
Unsecured notes - fixed rate
Schedule of Capitalization [Line Items]
Unsecured debt	$ 15,370	13,058
Unsecured notes - fixed rate | Minimum
Schedule of Capitalization [Line Items]
Interest rate (percent)	2.55%
Unsecured notes - fixed rate | Maximum
Schedule of Capitalization [Line Items]
Interest rate (percent)	7.70%
Unsecured notes - fixed rate | FES
Schedule of Capitalization [Line Items]
Unsecured debt	$ 2,215	2,373
Unsecured notes - fixed rate | FES | Minimum
Schedule of Capitalization [Line Items]
Interest rate (percent)	2.55%
Unsecured notes - fixed rate | FES | Maximum
Schedule of Capitalization [Line Items]
Interest rate (percent)	6.80%
Unsecured notes - variable rate
Schedule of Capitalization [Line Items]
Unsecured debt	$ 1,450	$ 1,200
Unsecured notes - variable rate | Minimum
Schedule of Capitalization [Line Items]
Interest rate (percent)	3.227%
Unsecured notes - variable rate | Maximum
Schedule of Capitalization [Line Items]
Interest rate (percent)	3.227%