Property, Plant, and Equipment (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Plant anticipated to be retired early	[1]	$ 133,268	$ 147,659
In-service utility plant, net		2,018,121	1,865,352
Construction work in progress		110,091	105,748
Total property, plant, and equipment		2,128,212	1,971,100
Columbia Units [Member]
Property, Plant and Equipment [Line Items]
Plant anticipated to be retired early	[2]	133,268	147,659
Impairment of Long-Lived Assets
Impairment of long-lived assets		0
Regulated Operation [Member]
Property, Plant and Equipment [Line Items]
In-service utility plant, gross		2,506,329	2,300,057
Less: Accumulated depreciation and amortization		726,289	673,669
In-service utility plant, net		1,780,040	1,626,388
Construction work in progress	[3]	107,724	101,529
Electric [Member] | Regulated Operation [Member]
Property, Plant and Equipment [Line Items]
In-service utility plant, gross	[4]	1,769,559	1,585,847
Gas [Member] | Regulated Operation [Member]
Property, Plant and Equipment [Line Items]
In-service utility plant, gross		603,502	566,551
Non Regulated Energy [Member] | Unregulated Operation [Member]
Property, Plant and Equipment [Line Items]
In-service utility plant, gross		321,951	318,443
Less: Accumulated depreciation and amortization		83,870	79,479
In-service utility plant, net		238,081	238,964
Construction work in progress		2,367	4,219
MGE [Member]
Property, Plant and Equipment [Line Items]
Plant anticipated to be retired early	[1]	133,268	147,659
In-service utility plant, net		2,018,149	1,865,380
Construction work in progress		110,091	105,748
Total property, plant, and equipment		2,128,240	1,971,128
MGE [Member] | Regulated Operation [Member]
Property, Plant and Equipment [Line Items]
In-service utility plant, gross		2,506,357	2,300,085
Less: Accumulated depreciation and amortization		726,289	673,669
In-service utility plant, net		1,780,068	1,626,416
Construction work in progress	[3]	107,724	101,529
MGE [Member] | Electric [Member] | Regulated Operation [Member]
Property, Plant and Equipment [Line Items]
In-service utility plant, gross	[4]	1,769,576	1,585,864
MGE [Member] | Gas [Member] | Regulated Operation [Member]
Property, Plant and Equipment [Line Items]
In-service utility plant, gross		603,513	566,562
MGE [Member] | Non Regulated Energy [Member] | Unregulated Operation [Member]
Property, Plant and Equipment [Line Items]
In-service utility plant, gross		321,951	318,443
Less: Accumulated depreciation and amortization		83,870	79,479
In-service utility plant, net		238,081	238,964
Construction work in progress		$ 2,367	$ 4,219

[1] An asset that will be retired in the near future and substantially in advance of its previously expected retirement date is subject to abandonment accounting. In the second quarter of 2021, the operator of Columbia received approval from MISO to retire Columbia Units 1 and 2. The co-owners intend to retire Unit 1 and Unit 2 by June 2026. Final timing and retirement dates are subject to change depending on operational, regulatory, and other factors. As of December 31, 2023, early retirement of Columbia was probable. "Plant anticipated to be retired early" in table above is the net book value of these generating units. Assets for Columbia Unit 1 and Unit 2 are currently included in rate base, and MGE continues to depreciate them on a straight-line basis using the composite depreciation rates approved by the PSCW that included retirement dates of 2029 for Unit 1 and Unit 2. If it becomes probable that regulators will disallow full recovery or a return on the remaining net book value of a generating unit that is either abandoned or probable of being abandoned, an impairment loss would be required. An impairment loss would be recorded to the extent that the remaining net book value of the generating unit exceeds the present value of the amount expected to be recovered from ratepayers. No impairment was recorded as of December 31, 2023.

[2] MGE and the other co-owners announced plans to retire Columbia, a two unit coal-fired generation facility located in Portage, Wisconsin. The co-owners intend to retire Unit 1 and Unit 2 by June 2026. Final timing and retirement dates are subject to change depending on operational, regulatory, and other factors. As of December 31, 2023 and 2022, early retirement of Columbia was probable. See Footnote 4 for further information.

[3] Includes Paris and Darien solar projects. See Footnote 6 for further information on renewable projects.

[4] Includes Badger Hollow II placed in service in December 2023. See Footnote 6 for further information on Badger Hollow II.