Property, Plant, and Equipment (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Plant anticipated to be retired early	[1]	$ 147,659	$ 158,983
In-service utility plant, net		1,865,352	1,828,171
Construction work in progress		105,748	50,603
Total property, plant, and equipment		1,971,100	1,878,774
Columbia Units [Member]
Property, Plant and Equipment [Line Items]
Plant anticipated to be retired early	[2]	147,659	158,983
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		2,300,057	2,221,906
Less: Accumulated depreciation and amortization		673,669	636,804
In-service utility plant, net		1,626,388	1,585,102
Construction work in progress	[3]	101,529	49,211
Electric [Member] | Regulated Operation [Member]
Property, Plant and Equipment [Line Items]
In-service utility plant, gross		1,585,847	1,516,533
Gas [Member] | Regulated Operation [Member]
Property, Plant and Equipment [Line Items]
In-service utility plant, gross		566,551	546,390
Non Regulated Energy [Member] | Unregulated Operation [Member]
Property, Plant and Equipment [Line Items]
In-service utility plant, gross		318,443	317,881
Less: Accumulated depreciation and amortization		79,479	74,812
In-service utility plant, net		238,964	243,069
Construction work in progress		4,219	1,392
MGE [Member]
Property, Plant and Equipment [Line Items]
Plant anticipated to be retired early	[1]	147,659	158,983
In-service utility plant, net		1,865,380	1,828,199
Construction work in progress		105,748	50,603
Total property, plant, and equipment		1,971,128	1,878,802
MGE [Member] | Regulated Operation [Member]
Property, Plant and Equipment [Line Items]
In-service utility plant, gross		2,300,085	2,221,934
Less: Accumulated depreciation and amortization		673,669	636,804
In-service utility plant, net		1,626,416	1,585,130
Construction work in progress	[3]	101,529	49,211
MGE [Member] | Electric [Member] | Regulated Operation [Member]
Property, Plant and Equipment [Line Items]
In-service utility plant, gross		1,585,864	1,516,550
MGE [Member] | Gas [Member] | Regulated Operation [Member]
Property, Plant and Equipment [Line Items]
In-service utility plant, gross		566,562	546,401
MGE [Member] | Non Regulated Energy [Member] | Unregulated Operation [Member]
Property, Plant and Equipment [Line Items]
In-service utility plant, gross		318,443	317,881
Less: Accumulated depreciation and amortization		79,479	74,812
In-service utility plant, net		238,964	243,069
Construction work in progress		$ 4,219	$ 1,392

[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, 2022, 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. The PSCW approved in its 2023 electric rate case limited reopener to revise the depreciation schedule for Columbia Unit 2 to 2029 to align with Unit 1. See Footnote 9 for further details on MGE's rate proceedings. 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, 2022.

[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, 2022 and 2021, early retirement of Columbia was probable. See Footnote 4 for further information.

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