Fair Value Measurements (Details 2) (USD $) In Millions, unless otherwise specified																																					6 Months Ended
	Jun. 30, 2012 FTRs	Dec. 31, 2011 FTRs	Dec. 31, 2010 FTRs	Jun. 30, 2012 FTRs FES	Dec. 31, 2011 FTRs FES	Dec. 31, 2010 FTRs FES	Jun. 30, 2012 Non Utility Generation contract		Dec. 31, 2011 Non Utility Generation contract		Dec. 31, 2010 Non Utility Generation contract		Jun. 30, 2012 Non Utility Generation contract JCP&L		Dec. 31, 2011 Non Utility Generation contract JCP&L		Dec. 31, 2010 Non Utility Generation contract JCP&L		Dec. 31, 2011 LCAPP Contracts		Dec. 31, 2010 LCAPP Contracts		Jun. 30, 2012 LCAPP Contracts JCP&L		Dec. 31, 2011 LCAPP Contracts JCP&L		Dec. 31, 2010 LCAPP Contracts JCP&L		Jun. 30, 2012 Model Level 3 FTRs	Jun. 30, 2012 Model Level 3 FTRs FES	Jun. 30, 2012 Model Level 3 Non Utility Generation contract		Jun. 30, 2012 Model Level 3 LCAPP Contracts		Jun. 30, 2012 Model Level 3 LCAPP Contracts JCP&L		Jun. 30, 2012 Model Level 3 Minimum FTRs	Jun. 30, 2012 Model Level 3 Minimum FTRs FES	Jun. 30, 2012 Model Level 3 Minimum Non Utility Generation contract MWh	Jun. 30, 2012 Model Level 3 Minimum Non Utility Generation contract JCP&L MWh	Jun. 30, 2012 Model Level 3 Minimum LCAPP Contracts	Jun. 30, 2012 Model Level 3 Minimum LCAPP Contracts JCP&L	Jun. 30, 2012 Model Level 3 Maximum FTRs	Jun. 30, 2012 Model Level 3 Maximum FTRs FES	Jun. 30, 2012 Model Level 3 Maximum Non Utility Generation contract MWh	Jun. 30, 2012 Model Level 3 Maximum Non Utility Generation contract JCP&L MWh	Jun. 30, 2012 Model Level 3 Maximum LCAPP Contracts	Jun. 30, 2012 Model Level 3 Maximum LCAPP Contracts JCP&L	Jun. 30, 2012 Model Level 3 Weighted Average [Member] FTRs	Jun. 30, 2012 Model Level 3 Weighted Average [Member] FTRs FES	Jun. 30, 2012 Model Level 3 Weighted Average [Member] Non Utility Generation contract MWh	Jun. 30, 2012 Model Level 3 Weighted Average [Member] Non Utility Generation contract JCP&L MWh	Jun. 30, 2012 Model Level 3 Weighted Average [Member] LCAPP Contracts	Jun. 30, 2012 Model Level 3 Weighted Average [Member] LCAPP Contracts JCP&L
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value	$ 3	$ (22)	$ 0	$ 2	$ (6)	$ 0	$ (293)	[1]	$ (292)	[1]	$ (344)	[1]	$ (121)	[1]	$ (143)	[1]	$ (227)	[1]	$ 0	[1]	$ 0	[1]	$ (145)	[1]	$ 0	[1]	$ 0	[1]	$ 3	$ 2	$ (293)	[1]	$ (145)	[1]	$ (145)	[1]
Fair Value Inputs, RTO Auction Clearing Prices																																					(3.60)	(3.6)					4.90	4.9					0.70	0.50
Fair Value Inputs, Generation																																							500	63,000					6,609,000	715,000					2,665,000	166,000
Fair Value Inputs, Power, Regional Prices																																							49.50	49.5	94.9	94.9			84.90	84.9	248.40	248.40			63.70	65.80	183.90	183.90

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