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 [Member]
Beginning balance, shares at Dec. 31, 2014		34,668
Beginning balance, value before adjustments at Dec. 31, 2014	$ 659,401			$ 308,007
Cumulative effect of new accounting principle at Dec. 31, 2014	(142)			(142)
Beginning balance, value at Dec. 31, 2014	659,259	$ 34,668	$ 316,268	307,865	$ 458
Increase (Decrease) In Stockholders' Equity [Roll Forward]
Net Income	31,757			31,757
Other comprehensive loss	(95)				(95)
Common stock dividends declared	(19,589)			(19,589)
Ending balance, shares at Jun. 30, 2015		34,668
Ending balance, value at Jun. 30, 2015	671,332	$ 34,668	316,268	320,033	363
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	33,178			33,178
Other comprehensive loss	(154)				(154)
Common stock dividends declared	(20,454)			(20,454)
Ending balance, shares at Jun. 30, 2016		34,668
Ending balance, value at Jun. 30, 2016	$ 703,028	$ 34,668	$ 316,268	$ 351,889	$ 203