Consolidated Statements of Common Stockholders' Equity (FirstEnergy Solutions Corp.) (USD $) In Millions, except Share data	Total	Common Stock	Accumulated Other Comprehensive Income (Loss)	Retained Earnings (Accumulated Deficit)	FES	FES Common Stock	FES Accumulated Other Comprehensive Income (Loss)	FES Retained Earnings (Accumulated Deficit)
Beginning Balance at Dec. 31, 2009		$ 31	$ 527	$ 3,012		$ 1,545	$ 65	$ 1,759
Beginning Balance, Shares at Dec. 31, 2009		304,835,407				7
NET INCOME	718				231			231
Unrealized gain (loss) on derivative hedges, net of income taxes			22				14
Change in unrealized gain on investments, net of income taxes			5				5
Pension and other postretirement benefits, net of income taxes			(129)				(22)
Consolidated tax benefit allocation						22
Ending Balance at Dec. 31, 2010		31	425	3,084		1,567	62	1,990
Ending Balance, Shares at Dec. 31, 2010		304,835,407				7
NET INCOME	47				45
Ending Balance at Mar. 31, 2011
Beginning Balance at Dec. 31, 2010		31	425	3,084		1,567	62	1,990
Beginning Balance, Shares at Dec. 31, 2010		304,835,407				7
NET INCOME	869				(59)			(59)
Unrealized gain (loss) on derivative hedges, net of income taxes			15				7
Change in unrealized gain on investments, net of income taxes			12				10
Pension and other postretirement benefits, net of income taxes			(26)				(3)
Consolidated tax benefit allocation						3
Ending Balance at Dec. 31, 2011	13,280	42	426	3,047	3,577	1,570	76	1,931
Ending Balance, Shares at Dec. 31, 2011	418,216,437	418,216,437			7	7
Beginning Balance at Sep. 30, 2011
NET INCOME	99				(253)
Ending Balance at Dec. 31, 2011	13,280	42		3,047	3,577
Ending Balance, Shares at Dec. 31, 2011	418,216,437	418,216,437			7
NET INCOME	306				122
Ending Balance at Mar. 31, 2012
Beginning Balance at Dec. 31, 2011	13,280	42	426	3,047	3,577	1,570	76	1,931
Beginning Balance, Shares at Dec. 31, 2011	418,216,437	418,216,437			7	7
NET INCOME	771				187			187
Unrealized gain (loss) on derivative hedges, net of income taxes			2				(6)
Change in unrealized gain on investments, net of income taxes			(4)				(3)
Pension and other postretirement benefits, net of income taxes			(39)				5
Stock-based compensation						2
Consolidated tax benefit allocation						1
Ending Balance at Dec. 31, 2012	13,084	42	385	2,888	3,763	1,573	72	2,118
Ending Balance, Shares at Dec. 31, 2012	418,216,437	418,216,437			7	7
Beginning Balance at Sep. 30, 2012
NET INCOME	(148)				(35)
Ending Balance at Dec. 31, 2012	$ 13,084	$ 42		$ 2,888	$ 3,763
Ending Balance, Shares at Dec. 31, 2012	418,216,437	418,216,437			7