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, 2021		36,163
Beginning 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 (loss)	34,420			34,420
Common stock dividends declared	(14,013)			(14,013)
Equity-based compensation plans and other	278		278
Ending balance, shares at Mar. 31, 2022		36,163
Ending balance, value at Mar. 31, 2022	1,048,153	$ 36,163	395,181	616,809	0
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