Schedule I - Condensed Parent Company Finanical Statements (Details-Notes 2) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
MGE [Member]
Dividends from affiliates [Line Items]
Dividends from affiliates	$ 26,648,000	$ 26,150,000	$ 19,318,000
Dividend restrictions [Abstract]
Dividend restriction - common equity ratio	55.00%
Dividend restriction based on common equity ratio	39,800,000
Common equity ratio	57.30%
Available for dividends under first mortgage bond covenants	260,200,000
MGE Construct [Member]
Dividends from affiliates [Line Items]
Dividends from affiliates	0	0	4,915,000
MGE Power West Campus [Member]
Dividends from affiliates [Line Items]
Dividends from affiliates	9,500,000	4,000,000	9,150,000
MGE Power Elm Road [Member]
Dividends from affiliates [Line Items]
Dividends from affiliates	43,000,000	52,028,000	0
MGE Transco [Member]
Dividends from affiliates [Line Items]
Dividends from affiliates	0	2,372,000	1,795,000
MGE Energy [Member]
Dividends from affiliates [Line Items]
Dividends from affiliates	$ 79,148,000	$ 84,550,000	$ 35,178,000