MGE Energy Inc Consolidated Statements of Common Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]
Beginning balance, shares at Dec. 31, 2015		34,668
Beginning balance, value at Dec. 31, 2015	$ 690,458	$ 34,668	$ 316,268	$ 339,165	$ 357
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income	17,028			17,028
Other comprehensive income (loss)	(164)				(164)
Common stock dividends declared	(10,227)			(10,227)
Ending balance, shares at Mar. 31, 2016		34,668
Ending balance, value at Mar. 31, 2016	697,095	$ 34,668	316,268	345,966	193
Beginning balance, shares at Dec. 31, 2016		34,668
Beginning balance, value at Dec. 31, 2016	724,088	$ 34,668	316,268	372,950	202
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income	19,300			19,300
Other comprehensive income (loss)	97				97
Common stock dividends declared	(10,660)			(10,660)
Ending balance, shares at Mar. 31, 2017		34,668
Ending balance, value at Mar. 31, 2017	$ 732,825	$ 34,668	$ 316,268	$ 381,590	$ 299