Taxes (Details 6) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
General Taxes
Total general taxes	$ 962	$ 978	$ 984
KWH excise
General Taxes
Total general taxes	194	219	230
State gross receipts
General Taxes
Total general taxes	226	240	251
Real and personal property
General Taxes
Total general taxes	393	368	328
Social security and unemployment
General Taxes
Total general taxes	112	110	126
Other
General Taxes
Total general taxes	37	41	49
FES
General Taxes
Total general taxes	128	138	136
FES | State gross receipts
General Taxes
Total general taxes	69	77	77
FES | Real and personal property
General Taxes
Total general taxes	39	40	35
FES | Social security and unemployment
General Taxes
Total general taxes	17	19	20
FES | Other
General Taxes
Total general taxes	$ 3	$ 2	$ 4