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, 2020		36,163,000
Beginning balance, value at Dec. 31, 2020	$ 976,000	$ 36,163	$ 394,408	$ 545,429	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	105,761			105,761
Common stock dividends declared	(54,788)			(54,788)
Equity-based compensation plans and other	495		495
Ending balance, shares at Dec. 31, 2021		36,163,000
Ending balance, value at Dec. 31, 2021	1,027,468	$ 36,163	394,903	596,402	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	110,952			110,952
Common stock dividends declared	(57,500)			(57,500)
Equity-based compensation plans and other	754		754
Ending balance, shares at Dec. 31, 2022		36,163,000
Ending 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