MGE Energy Inc Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Comprehensive Income [Abstract]
Net Income	$ 23,642		$ 21,038		$ 53,960		$ 51,544
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on available-for-sale securities, net of tax	(8)	[1]	(74)	[2]	35	[3]	7	[4]
Reclassification of realized gain on available-for-sale securities, net of tax	0	[5]	0	[5]	0	[5]	(15)	[6]
Comprehensive Income	$ 23,634		$ 20,964		$ 53,995		$ 51,536

[1] Net of $5 tax

[2] Net of $50 tax

[3] Net of $24 tax

[4] Net of $4 tax

[5] Net of $0 tax

[6] Net of $10 tax