Schedule I - Condensed Parent Company Finanical Statements (Details-Cash Flow Statement) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating Activities:
Cash Provided by (Used for) Operating Activities	$ 130,772	$ 124,033	$ 117,909
Investing Activities:
Other	1,873	149	(1,727)
Cash Provided by (Used for) Investing Activities	(66,351)	(57,385)	(79,975)
Financing Activities:
Issuance of common stock, net	0	0	6,275
Cash dividends paid on common stock	(35,026)	(34,370)	(33,693)
Change in short-term debt	(22,500)	(92,000)	(10,000)
Cash Provided by (Used for) Financing Activities	(30,362)	(64,242)	(37,336)
Change in Cash and Cash Equivalents:	34,059	2,406	598
Cash and cash equivalents at beginning of period	7,110	4,704	4,106
Cash and cash equivalents at end of period	41,169	7,110	4,704
MGE Energy [Member]
Operating Activities:
Cash Provided by (Used for) Operating Activities	50,696	48,430	16,469
Investing Activities:
Return of Investment - Affiliates	30,000	50,000	3,297
Other	(3,022)	(1,656)	(150)
Cash Provided by (Used for) Investing Activities	26,978	48,344	3,147
Financing Activities:
Issuance of common stock, net	0	0	6,275
Cash dividends paid on common stock	(35,026)	(34,370)	(33,693)
Change in short-term debt	(19,000)	(62,000)	7,500
Cash Provided by (Used for) Financing Activities	(54,026)	(96,370)	(19,918)
Change in Cash and Cash Equivalents:	23,648	404	(302)
Cash and cash equivalents at beginning of period	972	568	870
Cash and cash equivalents at end of period	$ 24,620	$ 972	$ 568