Fair Value Measurements (Details Textuals) (USD $)	3 Months Ended			0 Months Ended	3 Months Ended			3 Months Ended			3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Mar. 31, 2014 Revolving Credit Facility credit_facility	Mar. 31, 2014 NUG contracts	Mar. 31, 2014 FirstEnergy Revolving Credit Facility	Mar. 31, 2014 FE Revolving Credit Facility	Mar. 31, 2014 FES	Mar. 31, 2013 FES	Dec. 31, 2013 FES	Mar. 31, 2014 FES Revolving Credit Facility	Mar. 31, 2014 FES and AE Supply Revolving Credit Facility	Mar. 31, 2014 FET Revolving Credit Facility	Mar. 31, 2014 ATSI Revolving Credit Facility	Mar. 29, 2014 ATSI Revolving Credit Facility	Mar. 31, 2014 TrAIL Revolving Credit Facility	Mar. 29, 2014 TrAIL Revolving Credit Facility	Mar. 31, 2014 PCRB FG and NG	Mar. 31, 2014 PCRB FG	Mar. 31, 2014 PCRB NG	Apr. 02, 2014 PCRB PN Subsequent Event	Apr. 02, 2014 PCRB ME Subsequent Event	Mar. 31, 2014 Variable Rate Term Loan Due 2019 Term Loan FirstEnergy	Mar. 31, 2014 PRCB Put Date June 3, 2019 PCRB FG and NG	Mar. 31, 2014 PCRB Put Date December 3, 2018 PCRB FG and NG
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	$ 9,000,000		$ 10,000,000					$ 8,000,000		$ 9,000,000
Cash balance excluded from available for sale securities	324,000,000		204,000,000					276,000,000		135,000,000
Investments not required to be disclosed	635,000,000		636,000,000
Number of credit facilities extended				3
Increase (decrease) of maximum borrowing capacity						1,000,000,000	1,000,000,000					(1,000,000,000)
Line of Credit Facility, Maximum Borrowing Capacity						3,500,000,000.0	3,500,000,000.0					1,500,000,000.0	1,000,000,000	500,000,000	100,000,000	400,000,000	200,000,000
Loss on debt redemptions	7,000,000	117,000,000				5,000,000		5,000,000	71,000,000		3,000,000
Debt instrument, face amount																		417,000,000					1,000,000,000	182,000,000	235,000,000
Stated interest rate percentage																								4.00%	3.75%
Face amount of debt repurchased																			$ 197,000,000	$ 16,000,000	$ 45,000,000	$ 29,000,000