Schedule I - Condensed Parent Company Finanical Statements (Details-Comprehensive Income Statement) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Operating Expenses:
Other operations and maintenance									$ 171,248		$ 172,996		$ 165,859
Total Operating Expenses	129,301	100,199	103,791	129,609	117,655	97,950	92,140	120,815	462,900		428,560		438,514
Operating Income	25,962	39,900	24,497	37,628	19,350	39,888	25,081	28,444	127,987		112,763		107,868
Equity in earnings of investments									9,434		9,079		8,615
Income before income taxes									119,764		103,365		96,920
Income tax provision	(7,829)	(14,692)	(8,660)	(13,678)	(6,208)	(14,253)	(8,596)	(9,862)	(44,859)		(38,919)		(35,992)
Net Income	14,077	24,353	13,891	22,584	10,486	23,642	14,270	16,048	74,905		64,446		60,928
Other comprehensive income/(loss), net of tax:
Unrealized gain (loss) on available for sale securities, net of tax									283	[1]	(18)	[2]	(15)	[3]
Reclassification of realized gain on available-for-sale securities, net of tax									0	[4]	0	[4]	(15)	[3]
Comprehensive Income									75,188		64,428		60,898
MGE Energy [Member]
Operating Expenses:
Other operations and maintenance									613		649		718
Total Operating Expenses									613		649		718
Operating Income									(613)		(649)		(718)
Equity in earnings of investments									76,362		65,132		61,075
Other income/(loss), net									(1,863)		(496)		505
Other interest									55		45		(22)
Income before income taxes									73,941		64,032		60,840
Income tax provision									964		414		88
Net Income									74,905		64,446		60,928
Other comprehensive income/(loss), net of tax:
Unrealized gain (loss) on available for sale securities, net of tax									283	[1]	(18)	[2]	(15)	[3]
Reclassification of realized gain on available-for-sale securities, net of tax									0	[4]	0	[4]	(15)	[3]
Comprehensive Income									$ 75,188		$ 64,428		$ 60,898

[1] Net of $189 tax

[2] Net of $12 tax

[3] Net of $10 tax

[4] Net of $0 tax