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	25,812			25,812
Other comprehensive income/(loss):
Unrealized gain (loss) on available-for-sale securities, net of tax	(80)					(80)	[1]
Reclassification of realized gain on available-for-sale securities, net of tax	0
Common stock dividends declared	(17,030)			(17,030)	[2]
Ending balance, value at Jun. 30, 2010	510,497	23,114	316,268	170,990		125
Ending balance, shares at Jun. 30, 2010		23,114
Beginning balance, value at Mar. 31, 2010
Net Income	11,552
Other comprehensive income/(loss):
Unrealized gain (loss) on available-for-sale securities, net of tax	(88)
Reclassification of realized gain on available-for-sale securities, net of tax	0
Ending balance, value at Jun. 30, 2010	510,497	23,114	316,268
Ending balance, shares at Jun. 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	30,506			30,506
Other comprehensive income/(loss):
Unrealized gain (loss) on available-for-sale securities, net of tax	81					81	[1]
Reclassification of realized gain on available-for-sale securities, net of tax	(15)					(15)	[3]
Common stock dividends declared	(17,340)			(17,340)	[4]
Ending balance, value at Jun. 30, 2011	538,312	23,114	316,268	198,722		208
Ending balance, shares at Jun. 30, 2011		23,114
Beginning balance, value at Mar. 31, 2011
Net Income	12,723
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	(15)
Ending balance, value at Jun. 30, 2011	$ 538,312	$ 23,114	$ 316,268
Ending balance, shares at Jun. 30, 2011		23,114

[1] net of $54 tax

[2] $0.737 per share

[3] net of $10 tax

[4] $0.750 per share