MGE Energy Inc Consolidated Statements of Common Equity (Unaudited) - USD ($) $ 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, 2023		36,163,000
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		13,000
Issuance of common stock, net	0
Equity-based compensation plans and other	877	$ 13	864
Ending balance, shares at Jun. 30, 2024		36,176,000
Ending balance, value at Jun. 30, 2024	1,167,628	$ 36,176	397,614	733,838	0
Beginning balance, shares at Mar. 31, 2024		36,176,000
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		36,176,000
Ending balance, value at Jun. 30, 2024	1,167,628	$ 36,176	397,614	733,838	0
Beginning balance, shares at Dec. 31, 2024		36,490,000
Beginning balance, value at Dec. 31, 2024	1,230,138	$ 36,490	429,515	764,133	0
Ending balance, shares at Mar. 31, 2025		36,537,000
Ending balance, value at Mar. 31, 2025	1,258,913	$ 36,537	433,079	789,297	0
Beginning balance, shares at Dec. 31, 2024		36,490,000
Beginning balance, value at Dec. 31, 2024	1,230,138	$ 36,490	429,515	764,133	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	68,090			68,090
Common stock dividends declared	$ (32,872)			(32,872)
Stock Issued During Period, Shares, Dividend Reinvestment Plan	40,995	41,000
Stock Issued During Period, Value, Dividend Reinvestment Plan	$ 3,750	$ 41	3,709
Equity-based compensation plans and other - Shares		11,000
Issuance of common stock, net	3,750
Equity-based compensation plans and other	867	$ 11	856
Ending balance, shares at Jun. 30, 2025		36,542,000
Ending balance, value at Jun. 30, 2025	1,269,973	$ 36,542	434,080	799,351	0
Beginning balance, shares at Mar. 31, 2025		36,537,000
Beginning balance, value at Mar. 31, 2025	1,258,913	$ 36,537	433,079	789,297	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	26,498			26,498
Common stock dividends declared	(16,444)			(16,444)
Stock Issued During Period, Shares, Dividend Reinvestment Plan		5,000
Stock Issued During Period, Value, Dividend Reinvestment Plan	471	$ 5	466
Equity-based compensation plans and other	(535)		(535)
Ending balance, shares at Jun. 30, 2025		36,542,000
Ending balance, value at Jun. 30, 2025	$ 1,269,973	$ 36,542	$ 434,080	$ 799,351	$ 0