Discontinued Operations - Major Classes of Cash Flow Items from Discontinued Operations (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Income (loss) from discontinued operations	$ 1,192	$ (52)
Depreciation and amortization, including nuclear fuel, regulatory assets, net, intangible assets and deferred debt-related costs	280	416
Unrealized (gain) loss on derivative transactions	(10)	47
CASH FLOWS FROM INVESTING ACTIVITIES:
Property additions	(583)	(588)
Nuclear fuel	0	(132)
Sales of investment securities held in trusts	300	738
Purchases of investment securities held in trusts	(322)	(761)
FES and FENOC \| Discontinued Operations, Disposed of by Means Other than Sale
CASH FLOWS FROM OPERATING ACTIVITIES:
Income (loss) from discontinued operations	1,192	(52)
Depreciation and amortization, including nuclear fuel, regulatory assets, net, intangible assets and deferred debt-related costs	47	79
Unrealized (gain) loss on derivative transactions	(10)	47
CASH FLOWS FROM INVESTING ACTIVITIES:
Property additions	(15)	(90)
Nuclear fuel	0	(132)
Sales of investment securities held in trusts	109	231
Purchases of investment securities held in trusts	$ (122)	$ (245)

The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

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