MGE Energy Inc Consolidated Statements of Common Equity (Unaudited) (USD $) In Thousands, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]
Beginning balance, value at Dec. 31, 2012	$ 579,429	$ 34,668	$ 316,268	$ 228,399	$ 94
Beginning balance, shares at Dec. 31, 2012		34,668
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income	60,828			60,828
Other comprehensive income (loss)	176				176
Common stock dividends declared	(27,685)			(27,685)
Ending balance, value at Sep. 30, 2013	612,748	34,668	316,268	261,542	270
Ending balance, shares at Sep. 30, 2013		34,668
Beginning balance, value at Dec. 31, 2013	617,510	34,668	316,268	266,197	377
Beginning balance, shares at Dec. 31, 2013		34,668
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income	65,133			65,133
Other comprehensive income (loss)	56				56
Common stock dividends declared	(28,634)			(28,634)
Cash in lieu of fractional shares related to stock split	(80)			(80)
Ending balance, value at Sep. 30, 2014	$ 653,985	$ 34,668	$ 316,268	$ 302,616	$ 433
Ending balance, shares at Sep. 30, 2014		34,668