DISCONTINUED OPERATIONS - Major Classes of Cash Flow Items from Discontinued Operations (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Income from discontinued operations	[1]	$ 76	$ 8	$ 326
Gain on disposal, net of tax		(76)	(59)	(435)
Depreciation and amortization, including nuclear fuel, regulatory assets, net, intangible assets and deferred debt-related costs		1,199	1,217	1,384
Deferred income taxes and investment tax credits, net		113	252	485
CASH FLOWS FROM INVESTING ACTIVITIES:
Property additions		(2,657)	(2,665)	(2,675)
Sales of investment securities held in trusts		186	1,637	909
Purchases of investment securities held in trusts		(208)	(1,675)	(963)
FES and FENOC | Discontinued Operations, Disposed of by Means Other than Sale
CASH FLOWS FROM OPERATING ACTIVITIES:
Income from discontinued operations		76	8	326
Gain on disposal, net of tax		(76)	(59)	(435)
Depreciation and amortization, including nuclear fuel, regulatory assets, net, intangible assets and deferred debt-related costs		0	0	110
Deferred income taxes and investment tax credits, net		0	47	61
Unrealized (gain) loss on derivative transactions		0	0	(10)
CASH FLOWS FROM INVESTING ACTIVITIES:
Property additions		0	0	(27)
Sales of investment securities held in trusts		0	0	109
Purchases of investment securities held in trusts		$ 0	$ 0	$ (122)

[1] Net of income tax benefit of $59 million, $5 million, and $1.3 billion in 2020, 2019 and 2018, respectively.