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, 2020		36,163
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	34,933			34,933
Common stock dividends declared	(13,380)			(13,380)
Equity-based compensation plans and other	158		158
Ending balance, shares at Mar. 31, 2021		36,163
Ending balance, value at Mar. 31, 2021	997,711	$ 36,163	394,566	566,982	0
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	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