Summary of Significant Accounting Policies (Details-1) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Trade Receivables, Allowance for Doubtful Accounts, and Concentration Risk
Late payment charge on upaid receivables		1.00%
Accounts receivable, allowance for credit loss, writeoff		$ 3,600	$ 3,800
Accounts receivable, allowance for credit loss, period increase		3,300	3,900
Accounts receivable, allowance for credit loss		8,100	8,400
Allowance for Funds Used During Construction
AFUDC - borrowed funds		2,000	1,100	$ 1,700
AFUDC - equity funds		5,800	3,000	5,000
Capitalized Software Costs
Capitalized software		77,200	76,200
Capitalized software - accumulated amortization		63,900	53,400
Capitalized software - amortization		10,400	10,800	5,700
Capitalized Software Hosting Agreement Costs
Capitalized software hosting agreement		10,700	12,900
Capitalized software hosting agreement - accumulated amortization		11,400	8,500
Capitalized software hosting agreement - amortization expense		2,900	3,100	2,200
Tangible Asset Impairment Charges [Abstract]
Impairment, Long-Lived Asset, Held-for-Use		$ 0	0	0
Excise taxes
License fee tax rate, electric, retail sales		3.19%
License fee tax rate, electric, resale by purchaser		1.59%
License fee tax rate, natural gas		0.97%
License fee tax expense		$ 16,500	$ 14,700	$ 13,500
Minimum [Member]
Capitalized Software Hosting Agreement Costs
Capitalized software hosting agreement, useful life		3 years
Minimum [Member] | Capitalized Software [Member]
Property, Plant, and Equiptment
Property, plant, and equipment, useful life		3 years
Maximum [Member]
Capitalized Software Hosting Agreement Costs
Capitalized software hosting agreement, useful life		10 years
Maximum [Member] | Capitalized Software [Member]
Property, Plant, and Equiptment
Property, plant, and equipment, useful life		15 years
PSCW [Member]
Allowance for Funds Used During Construction
Authorized AFUDC rate		50.00%	50.00%	50.00%
Rate at which AFUDC was capitalized		7.11%	7.11%	6.89%
Authorized AFUDC rate - Signficiant projects (100%)		100.00%	100.00%	100.00%
Electric [Member]
Property, Plant, and Equiptment
Composite straight-line depreciation rates	[1]	3.80%	3.20%	3.20%
Gas [Member]
Property, Plant, and Equiptment
Composite straight-line depreciation rates		2.10%	2.10%	2.20%
Non Regulated Energy [Member]
Property, Plant, and Equiptment
Composite straight-line depreciation rates		2.30%	2.30%	2.40%
MGE Power Elm Road [Member]
Principles of Consolidation
Ownership percentage by parent		100.00%
MGE Power West Campus [Member]
Principles of Consolidation
Ownership percentage by parent		100.00%

[1] In the 2023 limited reopener, the PSCW approved new depreciation rates for Columbia effective January 1, 2023