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, 2019		34,668,000
Beginning balance, value at Dec. 31, 2019	$ 855,676	$ 34,668	$ 316,268	$ 504,740	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	92,418			92,418
Common stock dividends declared	(51,729)			(51,729)
Common stock issued during period		1,495,000
Issuance of common stock, net	79,635	$ 1,495	78,140
Ending balance, shares at Dec. 31, 2020		36,163,000
Ending 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
Issuance of common stock, net	0
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)
Issuance of common stock, net	0
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