Fair Value Measurements (Details 1) (USD $) In Millions, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2012		Dec. 31, 2011
Non Utility Generation contract
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Asset	$ 57	[1]	$ 122	[1]
Beginning Balance, Derivative Liability	(349)	[1]	(466)	[1]
Beginning Balance, Derivative, Total	(292)	[1]	(344)	[1]
Realized gain (loss), Derivative Asset	0	[1]	0	[1]
Realized gain (loss), Derivative Liability	0	[1]	0	[1]
Realized gain (loss), Derivative Total	0	[1]	0	[1]
Unrealized gain (loss), Derivative Asset	(39)	[1]	(58)	[1]
Unrealized gain (loss), Derivative Liability	(144)	[1]	(144)	[1]
Unrealized gain (loss), Derivative total	(183)	[1]	(202)	[1]
Purchases, Derivative Asset	0	[1]	0	[1]
Purchases, Derivative Liability	0	[1]	0	[1]
Purchases, Derivative Asset and Liability, total	0	[1]	0	[1]
Issuances, Derivative Asset	0	[1]	0	[1]
Issuances, Derivative Liability	0	[1]	0	[1]
Issuances, Derivative Asset and Liability, total	0	[1]	0	[1]
Sales, Derivative Asset	0	[1]	0	[1]
Sales, Derivative Liability	0	[1]	0	[1]
Sales, Derivative Asset and Liability, total	0	[1]	0	[1]
Settlements, Derivative Asset	0	[1]	(7)	[1]
Settlements, Derivative Liability	193	[1]	261	[1]
Settlements, Derivative Asset and Liability, total	193	[1]	254	[1]
Transfers into Level 3, Derivative Asset	0	[1]	0	[1]
Transfers into Level 3, Derivative Liability	0	[1]	0	[1]
Transfers into Level 3, Derivative Asset and Liability, total	0	[1]	0	[1]
Ending Balance, Derivative Asset	18	[1]	57	[1]
Ending Balance, Derivative Liability	(300)	[1]	(349)	[1]
Ending Balance, Derivative, Total	(282)	[1]	(292)	[1]
Non Utility Generation contract | JCP&L
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Asset	4		6	[1]
Beginning Balance, Derivative Liability	(147)		(233)	[1]
Beginning Balance, Derivative, Total	(143)		(227)
Realized gain (loss), Derivative Asset	0	[1]	0	[1]
Realized gain (loss), Derivative Liability	0	[1]	0	[1]
Realized gain (loss), Derivative Total	0		0
Unrealized gain (loss), Derivative Asset	(3)	[1]	(2)	[1]
Unrealized gain (loss), Derivative Liability	(17)	[1]	(11)	[1]
Unrealized gain (loss), Derivative total	(20)		(13)
Purchases, Derivative Asset	0	[1]	0	[1]
Purchases, Derivative Liability	0	[1]	0	[1]
Purchases, Derivative Asset and Liability, total	0		0
Issuances, Derivative Asset	0	[1]	0	[1]
Issuances, Derivative Liability	0	[1]	0	[1]
Issuances, Derivative Asset and Liability, total	0		0
Sales, Derivative Asset	0	[1]	0	[1]
Sales, Derivative Liability	0	[1]	0	[1]
Sales, Derivative Asset and Liability, total	0		0
Settlements, Derivative Asset	0	[1]	0	[1]
Settlements, Derivative Liability	39	[1]	97	[1]
Settlements, Derivative Asset and Liability, total	39		97
Transfers into Level 3, Derivative Asset	0	[1]	0	[1]
Transfers into Level 3, Derivative Liability	0	[1]	0	[1]
Transfers into Level 3, Derivative Asset and Liability, total	0		0
Ending Balance, Derivative Asset	1		4
Ending Balance, Derivative Liability	(125)		(147)
Ending Balance, Derivative, Total	(124)	[1]	(143)
LCAPP Contracts
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Asset	0	[1]
Beginning Balance, Derivative Liability	0	[1]
Beginning Balance, Derivative, Total	0	[1]	0	[1]
Realized gain (loss), Derivative Total	0	[1]	0	[1]
Unrealized gain (loss), Derivative total	3	[1]	0	[1]
Purchases, Derivative Asset and Liability, total	(145)	[1]	0	[1]
Issuances, Derivative Asset and Liability, total	0	[1]	0	[1]
Sales, Derivative Asset and Liability, total	0	[1]	0	[1]
Settlements, Derivative Asset and Liability, total	0	[1]	0	[1]
Transfers into Level 3, Derivative Asset and Liability, total	0	[1]	0	[1]
Ending Balance, Derivative Asset	0	[1]	0	[1]
Ending Balance, Derivative Liability	(142)	[1]	0	[1]
Ending Balance, Derivative, Total			0	[1]
LCAPP Contracts | JCP&L
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Asset	0		0	[1]
Beginning Balance, Derivative Liability	0		0	[1]
Beginning Balance, Derivative, Total	0		0
Realized gain (loss), Derivative Asset	0	[1]	0	[1]
Realized gain (loss), Derivative Liability	0	[1]	0	[1]
Realized gain (loss), Derivative Total	0		0
Unrealized gain (loss), Derivative Asset	0	[1]	0	[1]
Unrealized gain (loss), Derivative Liability	3	[1]	0	[1]
Unrealized gain (loss), Derivative total	3		0
Purchases, Derivative Asset	0	[1]	0	[1]
Purchases, Derivative Liability	(145)	[1]	0	[1]
Purchases, Derivative Asset and Liability, total	(145)		0
Issuances, Derivative Asset	0	[1]	0	[1]
Issuances, Derivative Liability	0	[1]	0	[1]
Issuances, Derivative Asset and Liability, total	0		0
Sales, Derivative Asset	0	[1]	0	[1]
Sales, Derivative Liability	0	[1]	0	[1]
Sales, Derivative Asset and Liability, total	0		0
Settlements, Derivative Asset	0	[1]	0	[1]
Settlements, Derivative Liability	0	[1]	0	[1]
Settlements, Derivative Asset and Liability, total	0		0
Transfers into Level 3, Derivative Asset	0	[1]	0	[1]
Transfers into Level 3, Derivative Liability	0	[1]	0	[1]
Transfers into Level 3, Derivative Asset and Liability, total	0		0
Ending Balance, Derivative Asset	0		0
Ending Balance, Derivative Liability	(142)		0
Ending Balance, Derivative, Total	(142)		0
FTRs
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Asset	1		0
Beginning Balance, Derivative Liability	(23)		0
Beginning Balance, Derivative, Total	(22)		0
Realized gain (loss), Derivative Asset	0		0
Realized gain (loss), Derivative Liability	0		0
Realized gain (loss), Derivative Total	0		0
Unrealized gain (loss), Derivative Asset	1		2
Unrealized gain (loss), Derivative Liability	(4)		(27)
Unrealized gain (loss), Derivative total	(3)		(25)
Purchases, Derivative Asset	12		13
Purchases, Derivative Liability	(10)		(4)
Purchases, Derivative Asset and Liability, total	2		9
Issuances, Derivative Asset	0		0
Issuances, Derivative Liability	0		0
Issuances, Derivative Asset and Liability, total	0		0
Sales, Derivative Asset	0		0
Sales, Derivative Liability	0		0
Sales, Derivative Asset and Liability, total	0		0
Settlements, Derivative Asset	(7)		(14)
Settlements, Derivative Liability	26		20
Settlements, Derivative Asset and Liability, total	19		6
Transfers into Level 3, Derivative Asset	0		0
Transfers into Level 3, Derivative Liability	0		(12)
Transfers into Level 3, Derivative Asset and Liability, total	0		(12)
Ending Balance, Derivative Asset	7		1
Ending Balance, Derivative Liability	(11)		(23)
Ending Balance, Derivative, Total	(4)		(22)
FTRs | FES
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Asset	1		0
Beginning Balance, Derivative Liability	(7)		0
Beginning Balance, Derivative, Total	(6)		0
Realized gain (loss), Derivative Asset	0		0
Realized gain (loss), Derivative Liability	0		0
Realized gain (loss), Derivative Total	0		0
Unrealized gain (loss), Derivative Asset	1		4
Unrealized gain (loss), Derivative Liability	(2)		(8)
Unrealized gain (loss), Derivative total	(1)		(4)
Purchases, Derivative Asset	8		2
Purchases, Derivative Liability	(7)		(1)
Purchases, Derivative Asset and Liability, total	1		1
Issuances, Derivative Asset	0		0
Issuances, Derivative Liability	0		0
Issuances, Derivative Asset and Liability, total	0		0
Sales, Derivative Asset	0		0
Sales, Derivative Liability	0		0
Sales, Derivative Asset and Liability, total	0		0
Settlements, Derivative Asset	(5)		(5)
Settlements, Derivative Liability	9		2
Settlements, Derivative Asset and Liability, total	4		(3)
Transfers into Level 3, Derivative Asset	0		0
Transfers into Level 3, Derivative Liability	0		0
Transfers into Level 3, Derivative Asset and Liability, total	0		0
Ending Balance, Derivative Asset	5		1
Ending Balance, Derivative Liability	(7)		(7)
Ending Balance, Derivative, Total	$ (2)		$ (6)

[1] Changes in the fair value of NUG and LCAPP contracts are generally subject to regulatory accounting treatment and do not impact earnings.