Derivative Instruments (Details Textuals) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Gains included in long-term debt associated with prior fixed-for-floating interest rate swap agreements	$ 32,000,000	$ 44,000,000
Unamortized gain (loss) on extinguishment of debt		17,000,000
Expected adverse change in quoted market prices of derivative instruments	10.00%
Decrease net income due to adverse change in commodity prices	1,000,000
Derivative Asset, Fair Value, Amount Offset Against Collateral	73,000,000	120,000,000
Period in which LSEs may request direct allocation of FTRs	2 years
Direct allocation of FTRs, cost	0
Commodity contracts
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	46,000,000	100,000,000
NUGs
Derivative [Line Items]
Liability position	151,000,000
Derivative Asset, Fair Value, Amount Offset Against Collateral	2,000,000	20,000,000
FTRs
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	25,000,000	0
Cash Flow Hedges
Derivative [Line Items]
Unamortized gains or losses associated with designated cash flow hedges	(8,000,000)	2,000,000
Gain (loss) on cash flow hedge expected to be reclassified to earnings in next twelve months	3,000,000
Unamortized gains or losses associated with prior interest rate hedges	50,000,000	59,000,000
Losses to be amortized to interest expenses during next twelve months	(9,000,000)
Number of forward starting swap agreements accounted for as a cash flow hedge outstanding	0	0
Fair Value Hedging
Derivative [Line Items]
Losses to be amortized to interest expenses during next twelve months	12,000,000
Reclassifications from long-term debt	12,000,000	19,000,000
Number of fixed-for-floating interest rate swap agreements outstanding	0	0
Interest rate swaps
Derivative [Line Items]
Number of interest rate swaps outstanding	0	0
FES | Commodity contracts
Derivative [Line Items]
Net asset position under commodity derivative contracts	5,000,000
Collateral posted	83,000,000
Additional collateral related to commodity derivatives	5,000,000
FES | FTRs
Derivative [Line Items]
Collateral posted	5,000,000
Derivative Asset, Fair Value, Amount Offset Against Collateral	$ 14,000,000