Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Income Tax Disclosure [Line Items]
Total unrecognized tax benefit	$ 2.3		$ 2.3		$ 3.2
Effective income tax rate	37.60%	37.60%	37.80%	37.70%
MGE [Member]
Income Tax Disclosure [Line Items]
Effective income tax rate	37.60%	37.60%	37.80%	37.70%