Fair Value Measurements (Details 6) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010
Non-utility Generation Contract and Financial Transfer Right Contracts [Member]
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Asset	$ 122	[1]	$ 200	[1]
Beginning Balance, Derivative Liability	(466)	[1]	(643)	[1]
Beginning Balance, Derivative, Total	(344)	[1]	(443)	[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	(55)	[1]	(71)	[1]
Unrealized gain (loss), Derivative Liability	173	[1]	110	[1]
Unrealized gain (loss), Derivative total	(228)	[1]	(181)	[1]
Purchases, Derivative Asset	13	[1]	0	[1]
Purchases, Derivative Liability	(4)	[1]	0	[1]
Purchases, Derivative Asset and Liability, total	9	[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	(23)	[1]	(7)	[1]
Settlements, Derivative Liability	(283)	[1]	(287)	[1]
Settlements, Derivative Asset and Liability, total	260	[1]	280	[1]
Transfers into Level 3, Derivative Asset	0	[1]	0	[1]
Transfers into Level 3, Derivative Liability	(12)	[1]	0	[1]
Transfers into Level 3, Derivative Asset and Liability, total	(12)	[1]	0	[1]
Ending Balance, Derivative Asset	57	[1]	122	[1]
Ending Balance, Derivative Liability	(372)	[1]	(466)	[1]
Ending Balance, Derivative, Total	(315)	[1]	(344)	[1]
Non Utility Generation Contract | JCP&L
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Asset	6	[2]	8	[2]
Beginning Balance, Derivative Liability	(233)	[2]	(399)	[2]
Beginning Balance, Derivative, Total	(227)	[2]	(391)	[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	(2)	[2]	(1)	[2]
Unrealized gain (loss), Derivative Liability	(11)	[2]	36	[2]
Unrealized gain (loss), Derivative total	(13)	[2]	35	[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]	(1)	[2]
Settlements, Derivative Liability	97	[2]	130	[2]
Settlements, Derivative Asset and Liability, total	97	[2]	129	[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]	6	[2]
Ending Balance, Derivative Liability	(147)	[2]	(233)	[2]
Ending Balance, Derivative, Total	(143)	[2]	(227)	[2]
Non Utility Generation Contract | Met-Ed
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Asset	112	[2]	176	[2]
Beginning Balance, Derivative Liability	(116)	[2]	(143)	[2]
Beginning Balance, Derivative, Total	(4)	[2]	33	[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	(57)	[2]	(59)	[2]
Unrealized gain (loss), Derivative Liability	(31)	[2]	(38)	[2]
Unrealized gain (loss), Derivative total	(88)	[2]	(97)	[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	(6)	[2]	(5)	[2]
Settlements, Derivative Liability	68	[2]	65	[2]
Settlements, Derivative Asset and Liability, total	62	[2]	60	[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	49	[2]	112	[2]
Ending Balance, Derivative Liability	(79)	[2]	(116)	[2]
Ending Balance, Derivative, Total	(30)	[2]	(4)	[2]
Non Utility Generation Contract | Penelec
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Asset	4	[2]	16	[2]
Beginning Balance, Derivative Liability	(117)	[2]	(101)	[2]
Beginning Balance, Derivative, Total	(113)	[2]	(85)	[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]	(11)	[2]
Unrealized gain (loss), Derivative Liability	(103)	[2]	(108)	[2]
Unrealized gain (loss), Derivative total	(103)	[2]	(119)	[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	(1)	[2]	(1)	[2]
Settlements, Derivative Liability	97	[2]	92	[2]
Settlements, Derivative Asset and Liability, total	96	[2]	91	[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	3	[2]	4	[2]
Ending Balance, Derivative Liability	(123)	[2]	(117)	[2]
Ending Balance, Derivative, Total	(120)	[2]	(113)	[2]
FTRs | FES
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Asset	0
Beginning Balance, Derivative Liability	0
Beginning Balance, Derivative, Total	0
Realized gain (loss), Derivative Asset	0
Realized gain (loss), Derivative Liability	0
Realized gain (loss), Derivative Total	0
Unrealized gain (loss), Derivative Asset	4
Unrealized gain (loss), Derivative Liability	8
Unrealized gain (loss), Derivative total	(4)
Purchases, Derivative Asset	2
Purchases, Derivative Liability	(1)
Purchases, Derivative Asset and Liability, total	1
Issuances, Derivative Asset	0
Issuances, Derivative Liability	0
Issuances, Derivative Asset and Liability, total	0
Sales, Derivative Asset	0
Sales, Derivative Liability	0
Sales, Derivative Asset and Liability, total	0
Settlements, Derivative Asset	(5)
Settlements, Derivative Liability	(2)
Settlements, Derivative Asset and Liability, total	(3)
Transfers into Level 3, Derivative Asset	0
Transfers into Level 3, Derivative Liability	0
Transfers into Level 3, Derivative Asset and Liability, total	0
Ending Balance, Derivative Asset	1
Ending Balance, Derivative Liability	(7)
Ending Balance, Derivative, Total	$ (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.