Consolidated Statements of Common Stockholders' Equity (FirstEnergy Corp.) (USD $) In Millions, except Share data	Total	Common Stock	Other Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings (Accumulated Deficit)
Beginning Balance at Dec. 31, 2009		$ 31	$ 5,448	$ 527	$ 3,012
Beginning Balance, Shares at Dec. 31, 2009		304,835,407
Earnings available to Parent	742				742
Unrealized gain (loss) on derivative hedges, net of income taxes				22
Change in unrealized gain on investments, net of income taxes				5
Pension and other postretirement benefits, net of income taxes				(129)
Stock-based compensation			(4)
Cash dividends declared on common stock					(670)
Ending Balance at Dec. 31, 2010		31	5,444	425	3,084
Beginning Balance, Shares at Dec. 31, 2010		304,835,407
Earnings available to Parent	885
Unrealized gain (loss) on derivative hedges, net of income taxes				15
Change in unrealized gain on investments, net of income taxes				12
Pension and other postretirement benefits, net of income taxes				(26)
Stock-based compensation			5
Allegheny merger, Shares		113,381,030
Allegheny merger		11	4,316
Cash dividends declared on common stock					(922)
Ending Balance at Dec. 31, 2011	13,280	42	9,765	426	3,047
Ending Balance, Shares at Dec. 31, 2011	418,216,437	418,216,437
Earnings available to Parent	770
Unrealized gain (loss) on derivative hedges, net of income taxes				2
Change in unrealized gain on investments, net of income taxes				(4)
Pension and other postretirement benefits, net of income taxes				(39)
Stock-based compensation			4
Cash dividends declared on common stock					(920)
Equity method adjustment (Note 8)					(9)
Ending Balance at Dec. 31, 2012	$ 13,084	$ 42	$ 9,769	$ 385	$ 2,888
Ending Balance, Shares at Dec. 31, 2012	418,216,437	418,216,437