Fair Value Measurements (Details 2) (Level 3, USD $) In Millions, unless otherwise specified																						9 Months Ended
	Sep. 30, 2014 FTRs	Dec. 31, 2013 FTRs	Dec. 31, 2012 FTRs	Sep. 30, 2014 FTRs FES	Dec. 31, 2013 FTRs FES	Dec. 31, 2012 FTRs FES	Sep. 30, 2014 Non Utility Generation Contract		Dec. 31, 2013 Non Utility Generation Contract		Dec. 31, 2012 Non Utility Generation Contract		Sep. 30, 2014 LCAPP Contracts		Dec. 31, 2013 LCAPP Contracts		Dec. 31, 2012 LCAPP Contracts		Sep. 30, 2014 Model FTRs	Sep. 30, 2014 Model FTRs FES	Sep. 30, 2014 Model Non Utility Generation Contract	Sep. 30, 2014 Model Minimum FTRs	Sep. 30, 2014 Model Minimum FTRs FES	Sep. 30, 2014 Model Minimum Non Utility Generation Contract MWh	Sep. 30, 2014 Model Maximum FTRs	Sep. 30, 2014 Model Maximum FTRs FES	Sep. 30, 2014 Model Maximum Non Utility Generation Contract MWh	Sep. 30, 2014 Model Weighted Average FTRs	Sep. 30, 2014 Model Weighted Average FTRs FES	Sep. 30, 2014 Model Weighted Average Non Utility Generation Contract MWh
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value	$ 24	$ (8)	$ (1)	$ 12	$ (8)	$ 0	$ (155)	[1]	$ (202)	[1]	$ (254)	[1]	$ 0	[1]	$ 0	[1]	$ (144)	[1]	$ 24	$ 12	$ (155)
Fair Value Inputs, RTO Auction Clearing Prices																						(4.60)	(4.60)		17.70	17.70		1.25	1.00
Fair Value Inputs, Power																								500			4,979,000			872,000
Fair Value Inputs, Power, Regional Prices																								45.60			69.80			52.30

[1] Changes in the fair value of NUG contracts are generally subject to regulatory accounting treatment and do not impact earnings.