Capitalization (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Schedule of Capitalization [Line Items]
Aggregate LOC Amount	818
Minimum
Schedule of Capitalization [Line Items]
Annual Fees	1.65%
Maximum
Schedule of Capitalization [Line Items]
Annual Fees	3.30%
FES
Schedule of Capitalization [Line Items]
Aggregate LOC Amount	744
FES | Minimum
Schedule of Capitalization [Line Items]
Annual Fees	1.65%
FES | Maximum
Schedule of Capitalization [Line Items]
Annual Fees	3.30%