Fair Value Measurements (Details Textuals) (USD $)	3 Months Ended		9 Months Ended			0 Months Ended		9 Months Ended	0 Months Ended	3 Months Ended		9 Months Ended			0 Months Ended		3 Months Ended	9 Months Ended		1 Months Ended				0 Months Ended	1 Months Ended				1 Months Ended								0 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	May 08, 2013 Revolving Credit Facility credit_facility	Oct. 31, 2013 Revolving Credit Facility Subsequent Event	Sep. 30, 2013 NUG contracts	May 08, 2013 FE Revolving Credit Facility	Sep. 30, 2013 FES	Sep. 30, 2012 FES	Sep. 30, 2013 FES	Sep. 30, 2012 FES	Dec. 31, 2012 FES	May 08, 2013 FES Revolving Credit Facility	Oct. 31, 2013 FES Corp and Allegheny Energy Inc Revolving Credit Facility Subsequent Event	Sep. 30, 2013 FGCO	Sep. 30, 2013 FGCO	Jun. 03, 2013 FGCO	Aug. 31, 2013 Ohio Funding Companies	Jun. 30, 2013 Ohio Funding Companies	Aug. 31, 2013 Ohio Funding Companies Minimum	Aug. 31, 2013 Ohio Funding Companies Maximum	May 08, 2013 JCP&L Revolving Credit Facility	Mar. 31, 2013 Senior Notes FE	Mar. 31, 2013 Senior Notes FES	Mar. 31, 2013 Senior Notes FES Year 2021	Mar. 31, 2013 Senior Notes FES Year 2039	Mar. 31, 2013 Senior Notes Allegheny Energy Inc	Mar. 31, 2013 Senior Notes Allegheny Energy Inc Year 2019	Mar. 31, 2013 Senior Notes Allegheny Energy Inc Year 2039	Mar. 31, 2013 Senior Notes FES Corp and Allegheny Energy Inc Minimum	Mar. 31, 2013 Senior Notes FES Corp and Allegheny Energy Inc Maximum	Mar. 31, 2013 Senior Notes, 2.75% Due 2018 Senior Notes FE	Mar. 31, 2013 Senior Notes, 4.25% Due 2023 Senior Notes FE	Mar. 31, 2013 Senior Notes, 3.50% Due 2023 Senior Notes Met-Ed	Apr. 15, 2013 Senior Notes, 4.80% Due 2015 Senior Notes FES	Mar. 31, 2013 Senior Notes, 4.80% Due 2015 Senior Notes FES	Jun. 30, 2013 Phase In Recovery Bonds Ohio Funding Companies	Aug. 31, 2013 Notes, 4.7% Due 2024 Unsecured Debt JCP&L	Mar. 31, 2013 Senior Notes, 4.95% Due 2013 Senior Notes, 3.50% Due 2023 Senior Notes Met-Ed	Jun. 30, 2013 Existing Taxable Bonds Ohio Funding Companies	Jun. 30, 2013 Existing Taxable Bonds Ohio Funding Companies Year 2013	Jun. 30, 2013 Existing Taxable Bonds Ohio Funding Companies Year 2015	Jun. 30, 2013 Existing Taxable Bonds Ohio Funding Companies Year 2020
Fair Value of Financial Instruments [Line Items]
Period of future observable data to determine contract price								3 years
Investment excludes Receivables, Payables and Accrued income	$ 13,000,000		$ 13,000,000		$ 110,000,000					$ 12,000,000		$ 12,000,000		$ 94,000,000
Cash balance excluded from available for sale securities	106,000,000		106,000,000		326,000,000					55,000,000		55,000,000		196,000,000
Investments not required to be disclosed	646,000,000		646,000,000		644,000,000
Debt instrument, face amount																									1,500,000,000									650,000,000	850,000,000	300,000,000			445,000,000	500,000,000		410,000,000	225,000,000	150,000,000	35,000,000
Stated interest rate percentage																						5.65%	7.25%									5.75%	6.80%	2.75%	4.25%	3.50%	4.80%	4.80%		4.70%	4.95%
Debt repurchased																										369,000,000	252,000,000	117,000,000	294,000,000	194,000,000	100,000,000						400,000,000
Face amount of debt repurchased																			235,000,000	660,000,000																					150,000,000
Payments of debt redemption premiums																										67,000,000			43,000,000								31,000,000
Debt repurchase notice amount																																						400,000,000
Loss on debt redemptions	9,000,000	0	(132,000,000)	0						0	0	(103,000,000)	0				0	0							119,000,000	71,000,000											32,000,000
Line of Credit Facility, Number of Credit Facilities Extended						3
Line of Credit Facility, Term, Extension Period									1 year						1 year									1 year
Line of Credit Facility, Increase, Borrowing Capacity									500,000,000						500,000,000									175,000,000
Line of Credit Facility, Current Borrowing Capacity							2,500,000,000.0		2,500,000,000						2,500,000,000	2,500,000,000.0								600,000,000
Line of Credit Facility, Amounts Excluded From Debt to Capital Ratio Calculation							1,400,000,000									785,700,000
Line of Credit Facility, Increase, Amounts Excluded From Debt to Capital Ratio Calculation							1,350,000,000.00
Weighted average interest rate on debt																																							2.48%			5.71%
Make-whole premiums paid on debt redemptions			$ 181,000,000	$ 0								$ 31,000,000	$ 0							$ 120,000,000	$ 30,000,000