MGE Energy Inc Consolidated Statements of Common Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss)/ Income [Member]
Beginning balance, shares at Dec. 31, 2022		36,163,000
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	117,699			117,699
Common stock dividends declared	(60,393)			(60,393)
Equity-based compensation plans and other	1,093		1,093
Ending balance, shares at Dec. 31, 2023		36,163,000
Ending 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	120,569			120,569
Common stock dividends declared	(63,596)			(63,596)
Stock Issued During Period, Shares, Dividend Reinvestment Plan		314,000
Stock Issued During Period, Value, Dividend Reinvestment Plan	31,700	$ 314	31,386
Equity-based compensation plans and other - Shares		13,000
Equity-based compensation plans and other	1,392	$ 13	1,379
Ending balance, shares at Dec. 31, 2024		36,490,000
Ending 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	135,889			135,889
Common stock dividends declared	$ (67,587)			(67,587)
Stock Issued During Period, Shares, Dividend Reinvestment Plan	41,000	41,000
Stock Issued During Period, Value, Dividend Reinvestment Plan	$ 3,750	$ 41	3,709
Equity-based compensation plans and other - Shares		11,000
Equity-based compensation plans and other	1,746	$ 11	1,735
Ending balance, shares at Dec. 31, 2025		36,542,000
Ending balance, value at Dec. 31, 2025	$ 1,303,936	$ 36,542	$ 434,959	$ 832,435	$ 0