MGE Energy Inc Consolidated Statements of Common Equity (Unaudited) (MGE Energy [Member], USD $) In Thousands	MGE Energy [Member] USD ($)	MGE Energy [Member] Common Stock [Member] USD ($)	MGE Energy [Member] Additional Paid-In Capital [Member] USD ($)	MGE Energy [Member] Retained Earnings [Member] USD ($)		MGE Energy [Member] Accumulated Other Comprehensive (Loss)/ Income [Member] USD ($)
Beginning balance, value at Dec. 31, 2009	$ 501,795	$ 23,114	$ 316,268	$ 162,208		$ 205
Beginning balance, shares at Dec. 31, 2009		23,114
Net Income	45,721			45,721
Other comprehensive income/(loss):
Unrealized gain (loss) on available-for-sale securities, net of tax	(71)					(71)	[1]
Reclassification of realized gain on available-for-sale securities, net of tax	0
Common stock dividends declared	(25,700)			(25,700)	[2]
Ending balance, value at Sep. 30, 2010	521,745	23,114	316,268	182,229		134
Ending balance, shares at Sep. 30, 2010		23,114
Beginning balance, value at Jun. 30, 2010
Net Income	19,909
Other comprehensive income/(loss):
Unrealized gain (loss) on available-for-sale securities, net of tax	9
Reclassification of realized gain on available-for-sale securities, net of tax	0
Ending balance, value at Sep. 30, 2010	521,745	23,114	316,268
Ending balance, shares at Sep. 30, 2010		23,114
Beginning balance, value at Dec. 31, 2010	525,080	23,114	316,268	185,556		142
Beginning balance, shares at Dec. 31, 2010		23,114
Net Income	51,544			51,544
Other comprehensive income/(loss):
Unrealized gain (loss) on available-for-sale securities, net of tax	7					7	[3]
Reclassification of realized gain on available-for-sale securities, net of tax	(15)					(15)	[4]
Common stock dividends declared	(26,183)			(26,183)	[5]
Ending balance, value at Sep. 30, 2011	550,433	23,114	316,268	210,917		134
Ending balance, shares at Sep. 30, 2011		23,114
Beginning balance, value at Jun. 30, 2011
Net Income	21,038
Other comprehensive income/(loss):
Unrealized gain (loss) on available-for-sale securities, net of tax	(74)
Reclassification of realized gain on available-for-sale securities, net of tax	0
Ending balance, value at Sep. 30, 2011	$ 550,433	$ 23,114	$ 316,268
Ending balance, shares at Sep. 30, 2011		23,114

[1] net of $48 tax

[2] $1.112 per share

[3] net of $4 tax

[4] net of $10 tax

[5] $1.133 per share