Regulatory Matters (Details Textuals) (Electric [Member], USD $) In Millions, unless otherwise specified			3 Months Ended
	Sep. 30, 2014	Jul. 30, 2012	Mar. 31, 2013 MPSC [Member]	Jan. 02, 2014 MPSC [Member]	Sep. 30, 2012 Refundable Revenue Decoupling [Member]
Public Utilities, General Disclosures [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