Fair Value Measurements (Details 1) (USD $) In Millions, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 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	(48)	[1]	(58)	[1]
Unrealized gain (loss), Derivative Liability	(86)	[1]	(144)	[1]
Unrealized gain (loss), Derivative total	(134)	[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	133	[1]	261	[1]
Settlements, Derivative Asset and Liability, total	133	[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	9	[1]	57	[1]
Ending Balance, Derivative Liability	(302)	[1]	(349)	[1]
Ending Balance, Derivative, Total	(293)	[1]	(292)	[1]
Non Utility Generation contract | JCP&L
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Asset	4	[1]	6	[1]
Beginning Balance, Derivative Liability	(147)	[1]	(233)	[1]
Beginning Balance, Derivative, Total	(143)	[1]	(227)	[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	0	[1]	(2)	[1]
Unrealized gain (loss), Derivative Liability	(7)	[1]	(11)	[1]
Unrealized gain (loss), Derivative total	(7)	[1]	(13)	[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]	0	[1]
Settlements, Derivative Liability	29	[1]	97	[1]
Settlements, Derivative Asset and Liability, total	29	[1]	97	[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	4	[1]	4	[1]
Ending Balance, Derivative Liability	(125)	[1]	(147)	[1]
Ending Balance, Derivative, Total	(121)	[1]	(143)	[1]
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	0	[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	(145)	[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	[1]	0	[1]
Beginning Balance, Derivative Liability	0	[1]	0	[1]
Beginning Balance, Derivative, Total	0	[1]	0	[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	0	[1]	0	[1]
Unrealized gain (loss), Derivative Liability	0	[1]	0	[1]
Unrealized gain (loss), Derivative total	0	[1]	0	[1]
Purchases, Derivative Asset	0	[1]	0	[1]
Purchases, Derivative Liability	(145)	[1]	0	[1]
Purchases, Derivative Asset and Liability, total	(145)	[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]	0	[1]
Settlements, Derivative Liability	0	[1]	0	[1]
Settlements, Derivative Asset and Liability, total	0	[1]	0	[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	0	[1]	0	[1]
Ending Balance, Derivative Liability	(145)	[1]	0	[1]
Ending Balance, Derivative, Total	(145)	[1]	0	[1]
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	0		2
Unrealized gain (loss), Derivative Liability	(2)		(27)
Unrealized gain (loss), Derivative total	(2)		(25)
Purchases, Derivative Asset	12		13
Purchases, Derivative Liability	(9)		(4)
Purchases, Derivative Asset and Liability, total	3		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	(1)		(14)
Settlements, Derivative Liability	25		20
Settlements, Derivative Asset and Liability, total	24		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	12		1
Ending Balance, Derivative Liability	(9)		(23)
Ending Balance, Derivative, Total	3		(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	0		4
Unrealized gain (loss), Derivative Liability	(1)		(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	(1)		(5)
Settlements, Derivative Liability	9		2
Settlements, Derivative Asset and Liability, total	8		(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	8		1
Ending Balance, Derivative Liability	(6)		(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.