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)	31,078			31,078
Common stock dividends declared	(14,736)			(14,736)
Equity-based compensation plans and other	354		354
Ending balance, shares at Mar. 31, 2023		36,163
Ending balance, value at Mar. 31, 2023	1,098,370	$ 36,163	396,011	666,196	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)	33,814			33,814
Common stock dividends declared	(15,460)			(15,460)
Equity-based compensation plans and other - Shares		13
Equity-based compensation plans and other	356	$ 13	343
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