Notes Payable to Banks, Commercial Paper, and Lines of Credit (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Short-Term Debt [Line Items]
Long-Term Line of Credit		$ 0
Short-term debt outstanding	[1]	38,000	$ 70,500
Letters of credit issued inside credit facilities	[1]	$ 685	$ 685
Weighted-average interest rate	[1]	5.40%	4.32%
Maximum short-term borrowings	[1]	$ 82,000	$ 70,500
Average short-term borrowings	[1]	$ 35,959	$ 20,177
Weighted-average interest rate during the year	[1]	4.94%	3.46%
MGE Energy unsecured committed revolving line of credit totaling $50 million [Member] | MGE Energy [Member]
Short-Term Debt [Line Items]
Line of credit		$ 50,000
Long-Term Line of Credit		0
Line of Credit [Member]
Short-Term Debt [Line Items]
Line of credit	[1],[2]	180,000	$ 150,000
Available capacity under line of credit	[1]	$ 141,315	$ 78,815
Debt covenant, required parent company ownership of MGE		100.00%
Line of Credit [Member] | Minimum [Member]
Short-Term Debt [Line Items]
Debt covenant, ownership interest by outside party resulting in repurchase of notes at par value		30.00%
Line of Credit [Member] | Maximum [Member]
Short-Term Debt [Line Items]
Debt to total capitalization ratio	[1],[3]	0.65	0.65
MGE [Member]
Short-Term Debt [Line Items]
Long-Term Line of Credit		$ 0
Short-term debt outstanding		38,000	$ 70,500
Letters of credit issued inside credit facilities		$ 685	$ 685
Weighted-average interest rate		5.40%	4.32%
Maximum short-term borrowings		$ 82,000	$ 70,500
Average short-term borrowings		$ 35,959	$ 20,177
Weighted-average interest rate during the year		4.94%	3.46%
MGE [Member] | Line of Credit [Member]
Short-Term Debt [Line Items]
Line of credit	[2]	$ 130,000	$ 100,000
Available capacity under line of credit		$ 91,315	$ 28,815
Debt covenant, required parent company ownership of MGE		100.00%
MGE [Member] | Line of Credit [Member] | Minimum [Member]
Short-Term Debt [Line Items]
Debt covenant, ownership interest by outside party resulting in repurchase of notes at par value		30.00%
MGE [Member] | Line of Credit [Member] | Maximum [Member]
Short-Term Debt [Line Items]
Debt to total capitalization ratio	[4]	0.65	0.65

[1] MGE Energy short-term borrowings include MGE Energy and MGE lines of credit and MGE commercial paper.

[2] As of December 31, 2023, MGE Energy and MGE had no borrowings outstanding under these credit facilities and were in compliance with the covenant requirements of the credit agreements.

[3] A change in control constitutes a default under the agreement. Change in control events are defined as (i) a failure by MGE Energy to hold 100% of the outstanding voting equity interest in MGE or (ii) the acquisition of beneficial ownership of 30% or more of the outstanding voting stock of MGE Energy by one person or two or more persons acting in concert.

[4] The ratio calculation excludes assets, liabilities, revenues, and expenses included in MGE's financial statements as the result of the consolidation of VIEs, such as MGE Power West Campus and MGE Power Elm Road. A change in control constitutes a default under the agreements. Change in control events are defined as (i) a failure by MGE Energy to hold 100% of the outstanding voting equity interest in MGE or (ii) the acquisition of beneficial ownership of 30% or more of the outstanding voting stock of MGE Energy by one person or two or more persons acting in concert.