Commitments, Guarantees and Contingencies (Details) $ in Millions	Dec. 31, 2016 USD ($)
Guarantor Obligations [Line Items]
Potential additional collateral obligations	$ 425
Regulated Distribution
Guarantor Obligations [Line Items]
Potential additional collateral obligations	150
FES
Guarantor Obligations [Line Items]
Potential additional collateral obligations	247
AE Supply
Guarantor Obligations [Line Items]
Potential additional collateral obligations	28
At Current Credit Rating
Guarantor Obligations [Line Items]
Potential additional collateral obligations	10
At Current Credit Rating | Regulated Distribution
Guarantor Obligations [Line Items]
Potential additional collateral obligations	0
At Current Credit Rating | FES
Guarantor Obligations [Line Items]
Potential additional collateral obligations	7
At Current Credit Rating | AE Supply
Guarantor Obligations [Line Items]
Potential additional collateral obligations	3
Upon Further Downgrade
Guarantor Obligations [Line Items]
Potential additional collateral obligations	48
Upon Further Downgrade | Regulated Distribution
Guarantor Obligations [Line Items]
Potential additional collateral obligations	48
Upon Further Downgrade | FES
Guarantor Obligations [Line Items]
Potential additional collateral obligations	0
Upon Further Downgrade | AE Supply
Guarantor Obligations [Line Items]
Potential additional collateral obligations	0
Surety Bond
Guarantor Obligations [Line Items]
Potential additional collateral obligations	367
Surety Bond | Regulated Distribution
Guarantor Obligations [Line Items]
Potential additional collateral obligations	102
Surety Bond | FES
Guarantor Obligations [Line Items]
Potential additional collateral obligations	240
Surety Bond | AE Supply
Guarantor Obligations [Line Items]
Potential additional collateral obligations	$ 25