Consolidated Statements of Comprehensive Income (Loss) (FirstEnergy Corp.) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
NET INCOME (LOSS)	$ (1,724)	$ (6,177)	$ 578
OTHER COMPREHENSIVE INCOME (LOSS):
Pension and OPEB prior service costs	(85)	(59)	(116)
Amortized losses on derivative hedges	10	8	5
Change in unrealized gain on available-for-sale securities	22	55	(11)
Other comprehensive income (loss)	(53)	4	(122)
Income taxes (benefits) on other comprehensive income (loss)	(21)	1	(47)
Other comprehensive income (loss), net of tax	(32)	3	(75)
COMPREHENSIVE INCOME (LOSS)	$ (1,756)	$ (6,174)	$ 503