Regulatory Matters (Details Textuals) (Electric [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2014	Jan. 02, 2014	Sep. 30, 2012	Jul. 30, 2012
Electric [Member]
Regulatory Asset and Liability [Line Items]
Defer the Reversal of RDM Liability				$ 127
Monthly Amount to Amortize from Liability to Income			10.6
PSCR Under-Recovery from Two Plan Years Prior	87
PSCR under-recovery from Three Plan Years Prior	148
Fermi 2 Production Level of Full Capacity					68.00%
Maximum of challenged Fermi 2 outage charges		$ 32