Commitments, Guarantees and Contingencies Commitments, Guarantees and Contingencies (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012
Guarantor Obligations [Line Items]
Maximum exposure under collateral provisions	$ 671
Credit Rating Downgrade to Below Investment Grade
Guarantor Obligations [Line Items]
Maximum exposure under collateral provisions	506
Material Adverse Event
Guarantor Obligations [Line Items]
Maximum exposure under collateral provisions	165
FES
Guarantor Obligations [Line Items]
Maximum exposure under collateral provisions	530
FES | Credit Rating Downgrade to Below Investment Grade
Guarantor Obligations [Line Items]
Maximum exposure under collateral provisions	439	[1]
Potential Acceleration Payments or Funding Obligations Due to Credit Rating Downgrade	222
FES | Material Adverse Event
Guarantor Obligations [Line Items]
Maximum exposure under collateral provisions	91	[2]
Potential Acceleration Payments or Funding Obligations Due to a Material Adverse Event	42
AE Supply
Guarantor Obligations [Line Items]
Maximum exposure under collateral provisions	68
AE Supply | Credit Rating Downgrade to Below Investment Grade
Guarantor Obligations [Line Items]
Maximum exposure under collateral provisions	8
AE Supply | Material Adverse Event
Guarantor Obligations [Line Items]
Maximum exposure under collateral provisions	60
Utilities
Guarantor Obligations [Line Items]
Maximum exposure under collateral provisions	73
Utilities | Credit Rating Downgrade to Below Investment Grade
Guarantor Obligations [Line Items]
Maximum exposure under collateral provisions	59	[1]
Potential Acceleration Payments or Funding Obligations Due to Credit Rating Downgrade	40
Utilities | Material Adverse Event
Guarantor Obligations [Line Items]
Maximum exposure under collateral provisions	$ 14

[1] Includes $222 million and $40 million that are also considered accelerations of payment or funding obligations for FES and the Utilities, respectively.

[2] Includes $42 million that is also considered an acceleration of payment or funding obligation for FES.