Rate Matters (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2012
Rate Proceedings [Abstract]
Authorized percentage increase (decrease) for electric		4.30%	2.30%
Authorized rate increase (decrease) for electric		$ 15.7	$ 8.0
Authorized percentage increase (decrease) for gas		0.30%	1.00%
Authorized rate increase (decrease) for gas		0.6	1.9
Fuel rules bandwidth			2.00%
Authorized return on common stock			10.30%
Utility common equity			58.10%
Proposed percent increase (decrease) for electric	5.80%
Proposed percent increase (decrease) for gas	2.60%
Fuel Rules [Abstract]
Electric fuel deferred costs upper threshold		102.00%
Electric fuel deferred costs lower threshold		98.00%
Increased (decreased) electric fuel costs deferred				(2.7)
Purchased Gas Adjustment [Abstract]
Purchased gas adjustment over collected			$ 0.9	$ 1.9