Schedule I - Condensed Parent Company Finanical Statements (Details-Income Statement) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating Expenses:
Other operations and maintenance									$ 165,859	$ 164,001	$ 145,177
Total Operating Expenses	113,507	97,238	94,062	133,707	115,575	93,586	88,960	137,868	438,514	435,989	449,154
Operating Income	17,439	36,334	23,197	30,898	20,353	34,352	20,122	21,775	107,868	96,602	84,665
Equity in earnings of investments									8,615	8,501	8,173
Income before income taxes									96,920	91,538	79,167
Income tax provision	(5,274)	(12,495)	(7,572)	(10,651)	(6,030)	(12,990)	(6,472)	(8,328)	(35,992)	(33,820)	(28,170)
Net Income	9,384	21,038	12,723	17,783	11,997	19,909	11,552	14,260	60,928	57,718	50,997
MGE Energy [Member]
Operating Expenses:
Other operations and maintenance									718	653	654
Total Operating Expenses									718	653	654
Operating Income									(718)	(653)	(654)
Equity in earnings of investments									61,075	59,147	50,742
Other income/(loss), net									505	(22)	(56)
Interest on long-term debt									0	0	2,766
Other interest									(22)	3	0
Income before income taxes									60,840	58,475	52,798
Income tax provision									88	(757)	(1,801)
Net Income									$ 60,928	$ 57,718	$ 50,997