Schedule I - Condensed Parent Company Finanical Statements (Details-Notes 2) (USD $)	0 Months Ended	12 Months Ended
	Dec. 20, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Dividends from Affiliates [Line Items]
Dividends from affiliates		$ 52,366,000	$ 44,343,000	$ 79,148,000
Stock Split
Stock split declared December 20, 2013, ratio (3:2)	1.5
First Mortgage Bonds [Member] | 7.70%, 2028 Series
Dividend Restrictions
Debt covenant, allowable amount available for payment of dividends		305,600,000
MGE [Member]
Dividends from Affiliates [Line Items]
Dividends from affiliates		25,000,000	20,404,000	26,648,000
Dividend Restrictions
Dividend restrictions, minimum common equity ratio		0.55
Common equity ratio		0.576
MGE [Member] | First Mortgage Bonds [Member] | 7.70%, 2028 Series
Dividend Restrictions
Debt covenant, allowable amount available for payment of dividends		305,600,000
MGE Construct [Member]
Dividends from Affiliates [Line Items]
Dividends from affiliates		0	239,000	0
MGE Power Elm Road [Member]
Dividends from Affiliates [Line Items]
Dividends from affiliates		17,300,000	16,000,000	43,000,000
MGE Power [Member]
Dividends from Affiliates [Line Items]
Dividends from affiliates		0	200,000	0
MGE Power West Campus [Member]
Dividends from Affiliates [Line Items]
Dividends from affiliates		9,250,000	7,500,000	9,500,000
MGE Transco [Member]
Dividends from Affiliates [Line Items]
Dividends from affiliates		$ 816,000	$ 0	$ 0