Fair Value Measurements (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 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	(14)	[1]	(58)	[1]
Unrealized gain (loss), Derivative Liability	(65)	[1]	(144)	[1]
Unrealized gain (loss), Derivative total	(79)	[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	(1)	[1]	(7)	[1]
Settlements, Derivative Liability	72	[1]	261	[1]
Settlements, Derivative Asset and Liability, total	71	[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	42	[1]	57	[1]
Ending Balance, Derivative Liability	(342)	[1]	(349)	[1]
Ending Balance, Derivative, Total	(300)	[1]	(292)	[1]
Non Utility Generation contract | JCP&L
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Asset	4	[2]	6	[2]
Beginning Balance, Derivative Liability	(147)	[2]	(233)	[2]
Beginning Balance, Derivative, Total	(143)	[2]	(227)	[2]
Realized gain (loss), Derivative Asset	0	[2]	0	[2]
Realized gain (loss), Derivative Liability	0	[2]	0	[2]
Realized gain (loss), Derivative Total	0	[2]	0	[2]
Unrealized gain (loss), Derivative Asset	0	[2]	(2)	[2]
Unrealized gain (loss), Derivative Liability	(6)	[2]	(11)	[2]
Unrealized gain (loss), Derivative total	(6)	[2]	(13)	[2]
Purchases, Derivative Asset	0	[2]	0	[2]
Purchases, Derivative Liability	0	[2]	0	[2]
Purchases, Derivative Asset and Liability, total	0	[2]	0	[2]
Issuances, Derivative Asset	0	[2]	0	[2]
Issuances, Derivative Liability	0	[2]	0	[2]
Issuances, Derivative Asset and Liability, total	0	[2]	0	[2]
Sales, Derivative Asset	0	[2]	0	[2]
Sales, Derivative Liability	0	[2]	0	[2]
Sales, Derivative Asset and Liability, total	0	[2]	0	[2]
Settlements, Derivative Asset	0	[2]	0	[2]
Settlements, Derivative Liability	17	[2]	97	[2]
Settlements, Derivative Asset and Liability, total	17	[2]	97	[2]
Transfers into Level 3, Derivative Asset	0	[2]	0	[2]
Transfers into Level 3, Derivative Liability	0	[2]	0	[2]
Transfers into Level 3, Derivative Asset and Liability, total	0	[2]	0	[2]
Ending Balance, Derivative Asset	4	[2]	4	[2]
Ending Balance, Derivative Liability	(136)	[2]	(147)	[2]
Ending Balance, Derivative, Total	(132)	[2]	(143)	[2]
FTRs
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Asset	1	[1]	0	[1]
Beginning Balance, Derivative Liability	(23)	[1]	0	[1]
Beginning Balance, Derivative, Total	(22)	[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]	2	[1]
Unrealized gain (loss), Derivative Liability	(3)	[1]	(27)	[1]
Unrealized gain (loss), Derivative total	(3)	[1]	(25)	[1]
Purchases, Derivative Asset	0	[1]	13	[1]
Purchases, Derivative Liability	0	[1]	(4)	[1]
Purchases, Derivative Asset and Liability, total	0	[1]	9	[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]	(14)	[1]
Settlements, Derivative Liability	11	[1]	20	[1]
Settlements, Derivative Asset and Liability, total	11	[1]	6	[1]
Transfers into Level 3, Derivative Asset	0	[1]
Transfers into Level 3, Derivative Liability	0	[1]	(12)	[1]
Transfers into Level 3, Derivative Asset and Liability, total	0	[1]	(12)	[1]
Ending Balance, Derivative Asset	1	[1]	1	[1]
Ending Balance, Derivative Liability	(15)	[1]	(23)	[1]
Ending Balance, Derivative, Total	(14)	[1]	(22)	[1]
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	0		2
Purchases, Derivative Liability	0		(1)
Purchases, Derivative Asset and Liability, total	0		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	0		(5)
Settlements, Derivative Liability	4		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	1		1
Ending Balance, Derivative Liability	(4)		(7)
Ending Balance, Derivative, Total	$ (3)		$ (6)

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

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