Fair Value (Details Textuals) (USD $)	3 Months Ended										3 Months Ended	12 Months Ended			3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Fair Value, Measurements, Recurring [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member]	Mar. 31, 2014 Restricted Assets [Member] Fair Value, Measurements, Recurring [Member]	Dec. 31, 2013 Restricted Assets [Member] Fair Value, Measurements, Recurring [Member]	Mar. 31, 2014 Other Investments [Member] Fair Value, Measurements, Recurring [Member]	Dec. 31, 2013 Other Investments [Member] Fair Value, Measurements, Recurring [Member]	Mar. 31, 2014 Other Investments [Member] Fair Value, Measurements, Recurring [Member] Equity [Member]	Dec. 31, 2013 Other Investments [Member] Fair Value, Measurements, Recurring [Member] Equity [Member]	Mar. 31, 2014 Nuclear Decommissioning Trust Fund [Member]	Dec. 31, 2013 Nuclear Decommissioning Trust Fund [Member]	Mar. 31, 2014 Fermi 2 [Member]	Dec. 31, 2013 Fermi 2 [Member]	Mar. 31, 2014 Fermi 1 [Member]	Mar. 31, 2013 Fermi 1 [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure			$ 58,000,000	$ 125,000,000	$ 43,000,000	$ 109,000,000	$ 15,000,000	$ 16,000,000			$ 13,000,000	$ 19,000,000
Available-for-sale Securities, Fair Value Disclosure									7,000,000	7,000,000
Other investments			138,000,000	136,000,000					138,000,000	136,000,000
Average Maturity of Debt Securities											7 years	7 years
Unrealized losses recognized as regulatory assets													33,000,000	31,000,000
Unrealized losses recognized in earnings															0	0
Unrealized on Available for Sale Securities	0	0
Trading Securities, Change in Unrealized Holding Gain (Loss)	$ 2,000,000	$ 8,000,000