Fair Value Measurements (Details 6) (USD $) In Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2011	Dec. 31, 2010
JCP&L | Non Utility Generation Contract
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Asset	$ 6	$ 8
Beginning Balance, Derivative Liability	(233)	(399)
Beginning Balance, Derivative, Total	(227)	(391)
Realized gain (loss), Derivative Asset
Realized gain (loss), Derivative Liability
Realized gain (loss), Derivative Total
Unrealized gain (loss), Derivative Asset	(1)	(1)
Unrealized gain (loss), Derivative Liability	(71)	36
Unrealized gain (loss), Derivative total	(72)	35
Purchases, Derivative Asset
Purchases, Derivative Liability
Purchases, Derivative Asset and Liability, total
Issuances, Derivative Asset
Issuances, Derivative Liability
Issuances, Derivative Asset and Liability, total
Sales, Derivative Asset
Sales, Derivative Liability
Sales, Derivative Asset and Liability, total
Settlements, Derivative Asset		(1)
Settlements, Derivative Liability	64	130
Settlements, Derivative Asset and Liability, total	64	129
Transfers into Level 3, Derivative Asset
Transfers into Level 3, Derivative Liability
Transfers into Level 3, Derivative Asset and Liability, total
Ending Balance, Derivative Asset	5	6
Ending Balance, Derivative Liability	(240)	(233)
Ending Balance, Derivative, Total	(235)	(227)
Met-Ed | Non Utility Generation Contract
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Asset	112	176
Beginning Balance, Derivative Liability	(116)	(143)
Beginning Balance, Derivative, Total	(4)	33
Realized gain (loss), Derivative Asset
Realized gain (loss), Derivative Liability
Realized gain (loss), Derivative Total
Unrealized gain (loss), Derivative Asset	(42)	(59)
Unrealized gain (loss), Derivative Liability	(36)	(38)
Unrealized gain (loss), Derivative total	(78)	(97)
Purchases, Derivative Asset
Purchases, Derivative Liability
Purchases, Derivative Asset and Liability, total
Issuances, Derivative Asset
Issuances, Derivative Liability
Issuances, Derivative Asset and Liability, total
Sales, Derivative Asset
Sales, Derivative Liability
Sales, Derivative Asset and Liability, total
Settlements, Derivative Asset	(4)	(5)
Settlements, Derivative Liability	30	65
Settlements, Derivative Asset and Liability, total	26	60
Transfers into Level 3, Derivative Asset
Transfers into Level 3, Derivative Liability
Transfers into Level 3, Derivative Asset and Liability, total
Ending Balance, Derivative Asset	66	112
Ending Balance, Derivative Liability	(122)	(116)
Ending Balance, Derivative, Total	(56)	(4)
Penelec | Non Utility Generation Contract
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Asset	4	16
Beginning Balance, Derivative Liability	(117)	(101)
Beginning Balance, Derivative, Total	(113)	(85)
Realized gain (loss), Derivative Asset
Realized gain (loss), Derivative Liability
Realized gain (loss), Derivative Total
Unrealized gain (loss), Derivative Asset		(11)
Unrealized gain (loss), Derivative Liability	(88)	(108)
Unrealized gain (loss), Derivative total	(88)	(119)
Purchases, Derivative Asset
Purchases, Derivative Liability
Purchases, Derivative Asset and Liability, total
Issuances, Derivative Asset
Issuances, Derivative Liability
Issuances, Derivative Asset and Liability, total
Sales, Derivative Asset
Sales, Derivative Liability
Sales, Derivative Asset and Liability, total
Settlements, Derivative Asset		(1)
Settlements, Derivative Liability	45	92
Settlements, Derivative Asset and Liability, total	45	91
Transfers into Level 3, Derivative Asset
Transfers into Level 3, Derivative Liability
Transfers into Level 3, Derivative Asset and Liability, total
Ending Balance, Derivative Asset	4	4
Ending Balance, Derivative Liability	(160)	(117)
Ending Balance, Derivative, Total	(156)	(113)
Non Utility Generation Contract
Reconciliation of changes in the fair value of NUG contracts
Beginning Balance, Derivative Asset	122	200
Beginning Balance, Derivative Liability	(466)	(643)
Beginning Balance, Derivative, Total	(344)	(443)
Realized gain (loss), Derivative Asset
Realized gain (loss), Derivative Liability
Realized gain (loss), Derivative Total
Unrealized gain (loss), Derivative Asset	(40)	(71)
Unrealized gain (loss), Derivative Liability	(203)	(110)
Unrealized gain (loss), Derivative total	(243)	(181)
Purchases, Derivative Asset	13
Purchases, Derivative Liability	(3)
Purchases, Derivative Asset and Liability, total	10
Issuances, Derivative Asset
Issuances, Derivative Liability
Issuances, Derivative Asset and Liability, total
Sales, Derivative Asset
Sales, Derivative Liability
Sales, Derivative Asset and Liability, total
Settlements, Derivative Asset	(6)	(7)
Settlements, Derivative Liability	154	287
Settlements, Derivative Asset and Liability, total	148	280
Transfers into Level 3, Derivative Asset
Transfers into Level 3, Derivative Liability	(12)
Transfers into Level 3, Derivative Asset and Liability, total	(12)
Ending Balance, Derivative Asset	89	122
Ending Balance, Derivative Liability	(530)	(466)
Ending Balance, Derivative, Total	(441)	(344)
FES | FTRs
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
Realized gain (loss), Derivative Liability
Realized gain (loss), Derivative Total
Unrealized gain (loss), Derivative Asset	1
Unrealized gain (loss), Derivative Liability
Unrealized gain (loss), Derivative total	1
Purchases, Derivative Asset	2
Purchases, Derivative Liability
Purchases, Derivative Asset and Liability, total	2
Issuances, Derivative Asset
Issuances, Derivative Liability
Issuances, Derivative Asset and Liability, total
Sales, Derivative Asset
Sales, Derivative Liability
Sales, Derivative Asset and Liability, total
Settlements, Derivative Asset	(1)
Settlements, Derivative Liability
Settlements, Derivative Asset and Liability, total	(1)
Transfers into Level 3, Derivative Asset
Transfers into Level 3, Derivative Liability
Transfers into Level 3, Derivative Asset and Liability, total
Ending Balance, Derivative Asset	2
Ending Balance, Derivative Liability	0
Ending Balance, Derivative, Total	$ 2