Fair Value (Details Textuals) (USD $)	3 Months Ended	6 Months Ended		3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended			12 Months Ended
	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Accumulated Net Unrealized Investment Gain (Loss) [Member]	Jun. 30, 2013 Accumulated Net Unrealized Investment Gain (Loss) [Member]	Jun. 30, 2014 Accumulated Net Unrealized Investment Gain (Loss) [Member]	Jun. 30, 2013 Accumulated Net Unrealized Investment Gain (Loss) [Member]	Jun. 30, 2014 Fermi 2 [Member]	Dec. 31, 2013 Fermi 2 [Member]	Jun. 30, 2014 Fermi 1 [Member]	Jun. 30, 2013 Fermi 1 [Member]	Jun. 30, 2014 Fermi 1 [Member]	Jun. 30, 2013 Fermi 1 [Member]	Jun. 30, 2014 Nuclear Decommissioning Trust Fund [Member]	Dec. 31, 2013 Nuclear Decommissioning Trust Fund [Member]	Jun. 30, 2014 Fair Value, Measurements, Recurring [Member]	Dec. 31, 2013 Fair Value, Measurements, Recurring [Member]	Jun. 30, 2014 Restricted Assets [Member] Fair Value, Measurements, Recurring [Member]	Dec. 31, 2013 Restricted Assets [Member] Fair Value, Measurements, Recurring [Member]	Jun. 30, 2014 Other Investments [Member] Fair Value, Measurements, Recurring [Member]	Dec. 31, 2013 Other Investments [Member] Fair Value, Measurements, Recurring [Member]	Jun. 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														$ 13,000,000	$ 19,000,000	$ 108,000,000	$ 125,000,000	$ 95,000,000	$ 109,000,000	$ 13,000,000	$ 16,000,000
Available-for-sale Securities, Fair Value Disclosure																						7,000,000	7,000,000
Other investments																						144,000,000	136,000,000
Average Maturity of Debt Securities														7 years	7 years
Unrealized losses recognized as regulatory assets								28,000,000	31,000,000
Unrealized losses recognized in earnings										0	0	0	0
Unrealized on Available for Sale Securities	(1,000,000)	(3,000,000)		0	0	0	0
Trading Securities, Realized Gain (Loss)		$ 8,000,000	$ 9,000,000