Derivative Instruments (Details 3) - Not Designated as Hedging Instrument - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified	$ 218	$ 161	$ 62
Purchase Power Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified	(131)	(130)	365
Other Operating Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Unrealized Gain (Loss) Recognized	(9)	73	(64)
Realized Gain (Loss) Reclassified	(35)	(49)	(44)
Fuel Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified	(8)	(34)	(6)
Interest Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified			14
Commodity contracts | Revenues
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified	210	111	(6)
Commodity contracts | Purchase Power Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified	(131)	(130)	365
Commodity contracts | Other Operating Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Unrealized Gain (Loss) Recognized	(14)	93	(86)
Realized Gain (Loss) Reclassified	0	0	0
Commodity contracts | Fuel Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified	(8)	(34)	(6)
Commodity contracts | Interest Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified			0
FTRs | Revenues
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified	8	50	68
FTRs | Purchase Power Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified	0	0	0
FTRs | Other Operating Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Unrealized Gain (Loss) Recognized	5	(20)	22
Realized Gain (Loss) Reclassified	(35)	(49)	(44)
FTRs | Fuel Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified	0	0	0
FTRs | Interest Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified			0
Interest rate swaps | Revenues
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified			0
Interest rate swaps | Purchase Power Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified			0
Interest rate swaps | Other Operating Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Unrealized Gain (Loss) Recognized			0
Realized Gain (Loss) Reclassified			0
Interest rate swaps | Fuel Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified			0
Interest rate swaps | Interest Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified			14
FES | Revenues
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified	218	160	61
FES | Purchase Power Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified	(131)	(130)	365
FES | Other Operating Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Unrealized Gain (Loss) Recognized	(9)	74	(65)
Realized Gain (Loss) Reclassified	(35)	(49)	(43)
FES | Commodity contracts | Revenues
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified	210	111	(6)
FES | Commodity contracts | Purchase Power Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified	(131)	(130)	365
FES | Commodity contracts | Other Operating Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Unrealized Gain (Loss) Recognized	(14)	93	(86)
Realized Gain (Loss) Reclassified	0	0	0
FES | FTRs | Revenues
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified	8	49	67
FES | FTRs | Purchase Power Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Realized Gain (Loss) Reclassified	0	0	0
FES | FTRs | Other Operating Expense
Effect of derivative instruments on the statements of income and comprehensive income for instruments not in hedging relationships
Unrealized Gain (Loss) Recognized	5	(19)	21
Realized Gain (Loss) Reclassified	$ (35)	$ (49)	$ (43)