Consolidated Statements of Common Stockholders' Equity (FirstEnergy Solutions Corp.) (USD $) In Millions, except Share data, unless otherwise specified	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, 2011		$ 42	$ 426	$ 3,047		$ 1,570	$ 76	$ 1,931
Beginning Balance, Shares at Dec. 31, 2011		418,216,437				7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
NET INCOME	771				187			187
Change in unrealized loss on derivative hedges, net of income taxes			2				(6)
Change in unrealized gain on investments, net of income taxes			(4)				(3)
Pensions and OPEB, net of income taxes			(39)				5
Stock-based compensation						2
Consolidated tax benefit allocation						1
Ending Balance at Dec. 31, 2012		42	385	2,888		1,573	72	2,118
Ending Balance, Shares at Dec. 31, 2012		418,216,437				7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
NET INCOME	196				2
Ending Balance at Mar. 31, 2013
Beginning Balance at Dec. 31, 2012		42	385	2,888		1,573	72	2,118
Beginning Balance, Shares at Dec. 31, 2012		418,216,437				7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
NET INCOME	392				60			60
Change in unrealized loss on derivative hedges, net of income taxes			2				(4)
Change in unrealized gain on investments, net of income taxes			(6)				(5)
Pensions and OPEB, net of income taxes			(97)				(9)
Equity contribution from parent						1,500
Stock-based compensation						1
Consolidated tax benefit allocation						6
Ending Balance at Dec. 31, 2013	12,692	42	284	2,590	5,312	3,080	54	2,178
Ending Balance, Shares at Dec. 31, 2013	418,628,559	418,628,559			7	7
Beginning Balance at Sep. 30, 2013
Increase (Decrease) in Stockholders' Equity [Roll Forward]
NET INCOME	142				89
Ending Balance at Dec. 31, 2013	12,692	42		2,590	5,312
Ending Balance, Shares at Dec. 31, 2013	418,628,559	418,628,559			7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
NET INCOME	208				13
Ending Balance at Mar. 31, 2014
Beginning Balance at Dec. 31, 2013	12,692	42	284	2,590	5,312	3,080	54	2,178
Beginning Balance, Shares at Dec. 31, 2013	418,628,559	418,628,559			7	7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
NET INCOME	299				(244)			(244)
Change in unrealized loss on derivative hedges, net of income taxes			(1)				(6)
Change in unrealized gain on investments, net of income taxes			16				13
Pensions and OPEB, net of income taxes			(53)				(4)
Equity contribution from parent						500
Stock-based compensation						7
Consolidated tax benefit allocation						7
Ending Balance at Dec. 31, 2014	12,420	42	246	2,285	5,585	3,594	57	1,934
Ending Balance, Shares at Dec. 31, 2014	421,102,570	421,102,570			7	7
Beginning Balance at Sep. 30, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
NET INCOME	(306)				(214)
Ending Balance at Dec. 31, 2014	$ 12,420	$ 42		$ 2,285	$ 5,585
Ending Balance, Shares at Dec. 31, 2014	421,102,570	421,102,570			7