Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Unrecognized tax benefits that would impact effective tax rate [Abstract]
Total unrecognized tax benefit	$ 2.5		$ 2.5		$ 2.4
Effective income tax rate [Line Items]
Effective income tax rate	37.60%	37.30%	37.80%	37.40%
MGE [Member]
Effective income tax rate [Line Items]
Effective income tax rate	37.60%	37.30%	37.80%	37.40%