MGE Energy Inc Consolidated Statements of Common Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss)/ Income [Member]
Beginning balance, shares at Dec. 31, 2012		34,668
Beginning balance, value at Dec. 31, 2012	$ 579,429	$ 34,668	$ 316,268	$ 228,399	$ 94
Increase (Decrease) in Common Equity [Roll Forward]
Net Income	74,905			74,905
Other comprehensive income/(loss)	283				283
Common stock dividends declared	(37,107)			(37,107)
Ending balance, shares at Dec. 31, 2013		34,668
Ending balance, value at Dec. 31, 2013	617,510	$ 34,668	316,268	266,197	377
Increase (Decrease) in Common Equity [Roll Forward]
Net Income	80,319			80,319
Other comprehensive income/(loss)	81				81
Common stock dividends declared	(38,429)			(38,429)
Cash in lieu of fractional shares related to stock split	(80)			(80)
Ending balance, shares at Dec. 31, 2014		34,668
Ending balance, value at Dec. 31, 2014	659,401	$ 34,668	316,268	308,007	458
Cumulative effect of new accounting principle (See Footnote 1) at Dec. 31, 2014	(142)			(142)
Beginning balance, value - Adjusted at Dec. 31, 2014	659,259			307,865
Increase (Decrease) in Common Equity [Roll Forward]
Net Income	71,343			71,343
Other comprehensive income/(loss)	(101)				(101)
Common stock dividends declared	(40,043)			(40,043)
Ending balance, shares at Dec. 31, 2015		34,668
Ending balance, value at Dec. 31, 2015	$ 690,458	$ 34,668	$ 316,268	$ 339,165	$ 357