Consolidated Statements of Comprehensive Income (Loss) (FirstEnergy Corp.) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 380	$ 395	$ (381)	$ 804
OTHER COMPREHENSIVE INCOME (LOSS):
Pension and OPEB prior service costs	(18)	(31)	(54)	(94)
Amortized (gains) losses on derivative hedges	2	2	6	4
Change in unrealized gains on available-for-sale securities	4	(11)	67	(21)
Other comprehensive income (loss)	(12)	(40)	19	(111)
Income taxes (benefits) on other comprehensive income (loss)	(5)	(15)	6	(42)
Other comprehensive income (loss), net of tax	(7)	(25)	13	(69)
COMPREHENSIVE INCOME (LOSS)	$ 373	$ 370	$ (368)	$ 735