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	36,475			36,475
Other comprehensive income (loss)	140				140
Common stock dividends declared	(18,264)			(18,264)
Ending balance, value at Jun. 30, 2013	597,780	34,668	316,268	246,610	234
Ending balance, shares at Jun. 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	41,804			41,804
Other comprehensive income (loss)	(39)				(39)
Common stock dividends declared	(18,840)			(18,840)
Cash in lieu of fractional shares related to stock split	(80)			(80)
Ending balance, value at Jun. 30, 2014	$ 640,355	$ 34,668	$ 316,268	$ 289,081	$ 338
Ending balance, shares at Jun. 30, 2014		34,668