Fair Value (Details Textuals) (USD $) In Millions, unless otherwise specified	9 Months Ended		3 Months Ended		9 Months Ended				9 Months Ended	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Accumulated Net Unrealized Investment Gain (Loss) [Member]	Sep. 30, 2013 Accumulated Net Unrealized Investment Gain (Loss) [Member]	Sep. 30, 2014 Accumulated Net Unrealized Investment Gain (Loss) [Member]	Sep. 30, 2013 Accumulated Net Unrealized Investment Gain (Loss) [Member]	Sep. 30, 2014 Fermi 2 [Member]	Dec. 31, 2013 Fermi 2 [Member]	Sep. 30, 2014 Nuclear Decommissioning Trust Fund [Member]	Dec. 31, 2013 Nuclear Decommissioning Trust Fund [Member]	Sep. 30, 2014 Fair Value, Measurements, Recurring [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member]	Sep. 30, 2014 Restricted Assets [Member] Fair Value, Measurements, Recurring [Member]	Dec. 31, 2013 Restricted Assets [Member] Fair Value, Measurements, Recurring [Member]	Sep. 30, 2014 Other Investments [Member] Fair Value, Measurements, Recurring [Member]	Dec. 31, 2013 Other Investments [Member] Fair Value, Measurements, Recurring [Member]	Sep. 30, 2014 Other Investments [Member] Fair Value, Measurements, Recurring [Member] Equity [Member]	Dec. 31, 2013 Other Investments [Member] Fair Value, Measurements, Recurring [Member] Equity [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure									$ 16	$ 19	$ 62	$ 125	$ 46	$ 109	$ 16	$ 16
Available-for-sale Securities, Fair Value Disclosure																	7	7
Other investments																	146	136
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	0	0
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount	0	0
Fair Value, Liabilities, Level 1 to Level 2 Transfers, Amount	0	0
Fair Value, Liabilities, Level 2 to Level 1 Transfers, Amount	0	0
Average Maturity of Debt Securities									7 years	7 years
Unrealized losses recognized as regulatory assets							37	31
Unrealized losses on Available for Sale Securities			0	0	0	0
Trading Securities, Realized Gain (Loss)	$ 9	$ 14