Common Equity (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2024 USD ($) $ / shares shares	Dec. 31, 2023 USD ($) $ / shares	Dec. 31, 2022 USD ($) $ / shares
Class of Stock [Line Items]
Common stock dividends declared	$ 63,596	$ 60,393	$ 57,500
Common stock dividends declared (in dollars per share) | $ / shares	$ 1.76	$ 1.67	$ 1.59
Stock Issued During Period, Shares, Dividend Reinvestment Plan | shares	314,000
Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan	$ 31,600
Dilutive securities | shares	28,589
MGE [Member]
Class of Stock [Line Items]
Cash dividends paid to parent by MGE	$ 34,500	$ 41,000
MGE [Member] | Minimum [Member]
Class of Stock [Line Items]
Dividend restrictions, common equity ratio	0.55