Pension and Other Postemployment Benefits (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Pensions
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	$ 42	$ 49
Interest costs	100	93
Expected return on plan assets	(115)	(125)
Amortization of prior service cost (credit)	2	3
Net periodic costs (credits)	29	20
OPEB
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	2	3
Interest costs	10	9
Expected return on plan assets	(8)	(8)
Amortization of prior service cost (credit)	(44)	(50)
Net periodic costs (credits)	(40)	(46)
FirstEnergy | Pensions
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit expense (credit)	21	11
FirstEnergy | OPEB
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit expense (credit)	(27)	(30)
FES | Pensions
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic costs (credits)	4	5
Net periodic benefit expense (credit)	4	3
FES | OPEB
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic costs (credits)	(5)	(5)
Net periodic benefit expense (credit)	$ (4)	$ (3)