Asset Retirement Obligations (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Fair values of the decommissioning trust assets
Legally restricted decommissioning assets	$ 2,204	$ 2,112
Changes to the asset retirement obligations
Beginning Balance	1,497	1,407
Liabilities assumed from Allegheny merger		60
Liabilities settled	(2)	(15)	[1]
Accretion	104	97
Revisions in estimated cash flows		(52)	[2]
Ending Balance	1,599	1,497
Asset Retirement Obligations (Textuals) [Abstract]
Reduced ARO liability resulting from deconsolidation		10
FES
Fair values of the decommissioning trust assets
Legally restricted decommissioning assets	1,283	1,223
Changes to the asset retirement obligations
Beginning Balance	904	892
Liabilities assumed from Allegheny merger		0
Liabilities settled	(1)	(1)
Accretion	62	59
Revisions in estimated cash flows		(46)	[2]
Ending Balance	965	904
OE
Fair values of the decommissioning trust assets
Legally restricted decommissioning assets	141	137
Changes to the asset retirement obligations
Beginning Balance	71	74
Liabilities assumed from Allegheny merger		0
Liabilities settled	0	(2)
Accretion	5	5
Revisions in estimated cash flows		(6)	[2]
Ending Balance	76	71
JCP&L
Fair values of the decommissioning trust assets
Legally restricted decommissioning assets	201	193
Changes to the asset retirement obligations
Beginning Balance	115	108
Liabilities assumed from Allegheny merger		0
Liabilities settled	0	0
Accretion	8	7
Revisions in estimated cash flows		0	[2]
Ending Balance	$ 123	$ 115

[1] Includes approximately $10 million in reduced ARO liabilities for FirstEnergy as a result of deconsolidation of the Signal Peak joint venture (See Note 7, Variable Interest Entities).

[2] During 2011, studies were completed to reassess the estimated cost of decommissioning the Perry and Davis-Besse nuclear generating facilities. The cost studies resulted in revisions to the estimated cash flows associated with the ARO liabilities and reduced the discounted liabilities as shown.