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]	AOCI Attributable to Parent [Member]
Beginning balance, shares at Dec. 31, 2022		36,163
Beginning balance, value at Dec. 31, 2022	$ 1,081,674	$ 36,163	$ 395,657	$ 649,854	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	59,759			59,759
Common stock dividends declared	(29,473)			(29,473)
Equity-based compensation plans and other	624		624
Ending balance, shares at Jun. 30, 2023		36,163
Ending balance, value at Jun. 30, 2023	1,112,584	$ 36,163	396,281	680,140	0
Beginning balance, shares at Mar. 31, 2023		36,163
Beginning balance, value at Mar. 31, 2023	1,098,370	$ 36,163	396,011	666,196	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	28,681			28,681
Common stock dividends declared	(14,737)			(14,737)
Equity-based compensation plans and other	270		270
Ending balance, shares at Jun. 30, 2023		36,163
Ending balance, value at Jun. 30, 2023	1,112,584	$ 36,163	396,281	680,140	0
Beginning balance, shares at Dec. 31, 2023		36,163
Beginning balance, value at Dec. 31, 2023	1,140,073	$ 36,163	396,750	707,160	0
Ending balance, shares at Mar. 31, 2024		36,176
Ending balance, value at Mar. 31, 2024	1,158,783	$ 36,176	397,093	725,514	0
Beginning balance, shares at Dec. 31, 2023		36,163
Beginning balance, value at Dec. 31, 2023	1,140,073	$ 36,163	396,750	707,160	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	57,608			57,608
Common stock dividends declared	(30,930)			(30,930)
Equity-based compensation plans and other - Shares		13
Equity-based compensation plans and other	877	$ 13	864
Ending balance, shares at Jun. 30, 2024		36,176
Ending balance, value at Jun. 30, 2024	1,167,628	$ 36,176	397,614	733,838	0
Beginning balance, shares at Mar. 31, 2024		36,176
Beginning balance, value at Mar. 31, 2024	1,158,783	$ 36,176	397,093	725,514	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	23,794			23,794
Common stock dividends declared	(15,470)			(15,470)
Equity-based compensation plans and other	521		521
Ending balance, shares at Jun. 30, 2024		36,176
Ending balance, value at Jun. 30, 2024	$ 1,167,628	$ 36,176	$ 397,614	$ 733,838	$ 0