Discontinued Operations - Major Classes of Assets and Liabilities as Discontinued Operations (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total current assets	$ 2	$ 606
Property, plant and equipment	353	1,057
Total current liabilities	0	973
Total noncurrent liabilities	0	3,399
FES and FENOC | Discontinued Operations, Disposed of by Means Other than Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash	0	1
Restricted cash	0	3
Receivables	0	202
Materials and supplies	2	201
Collateral	0	130
Other current assets	0	69
Total current assets	2	606
Property, plant and equipment	353	1,057
Investments	0	1,875
Other non-current assets	0	356
Total non-current assets	353	3,288
Total assets included in discontinued operations	355	3,894
Currently payable long-term debt	0	524
Accounts payable	0	200
Accrued taxes	0	38
Accrued compensation and benefits	0	79
Other current liabilities	0	132
Total current liabilities	0	973
Long-term debt and other long-term obligations	0	2,299
Accumulated deferred income taxes	0	(1,812)
Asset retirement obligations	0	1,945
Deferred gain on sale and leaseback transaction	0	723
Other non-current liabilities	0	244
Total noncurrent liabilities	0	3,399
Total liabilities included in discontinued operations	$ 0	$ 4,372