Elm Road (Details) (USD $)	12 Months Ended
	Dec. 31, 2011
Elm Road [Line Items]
Total liquidated damages	$ 250,000
MGE's share of liquidated damages	21,000
Loss Contingency, Settlement Agreement, Terms	Pursuant to the terms of the 2009 settlement agreement and a change order signed concurrent with the turnover of Unit 2, Bechtel was granted total schedule relief of 120 days for Unit 1 and 81 days for Unit 2. Therefore, Bechtel is responsible for 5 days of liquidated damages for Unit 1 and 23 days for Unit 2.
Elm Road Units [Member]
Elm Road [Line Items]
Elm Road placed in-service	195,900,000
Estimated total project cost over-run	181,000,000
Estimated ratio of total cost over-run to approved project costs	8.30%
MGE's Share of the estimated total project cost over-run	$ 14,000,000
Cap on construction cost above approved project cost	5.00%
MGE Power Elm Road [Member] | Elm Road Units [Member]
Elm Road Units ownership [Line Items]
Ownership interest in jointly owned plant	8.33%
Plant capacity - MW	615