Fair Value Measurements (Details 3) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	$ 1,808	$ 1,724
Unrealized Gain	25	27
Fair Value	1,833	1,751
Equity securities
Amortized cost basis, unrealized gains and losses and fair values of investments in available-for-sale securities
Cost Basis	664	533
Unrealized Gains	(33)	(58)
Fair Value	697	591
FES | Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	824	788
Unrealized Gain	13	13
Fair Value	837	801
FES | Equity securities
Amortized cost basis, unrealized gains and losses and fair values of investments in available-for-sale securities
Cost Basis	462	329
Unrealized Gains	(19)	(31)
Fair Value	$ 481	$ 360