Fair Value of Financial Instruments (Details-1) - USD ($) $ in Thousands		Dec. 31, 2020	Dec. 31, 2019
Liabilities:
Unamortized discount and debt issuance costs, net		$ 4,146	$ 4,479
Carrying Amount [Member]
Assets:
Cash and cash equivalents		44,738	23,481
Liabilities:
Short-term debt - commercial paper		52,500	0
Long-Term debt	[1]	528,220	547,879
Fair Value [Member]
Assets:
Cash and cash equivalents		44,738	23,481
Liabilities:
Short-term debt - commercial paper		52,500	0
Long-Term debt	[1]	639,271	611,909
MGE [Member] | Fair Value Disclosure Item Amounts [Domain]
Liabilities:
Unamortized discount and debt issuance costs, net		4,146	4,479
MGE [Member] | Carrying Amount [Member]
Assets:
Cash and cash equivalents		4,103	3,196
Liabilities:
Short-term debt - commercial paper		52,500	0
Long-Term debt	[1]	528,220	547,879
MGE [Member] | Fair Value [Member]
Assets:
Cash and cash equivalents		4,103	3,196
Liabilities:
Short-term debt - commercial paper		52,500	0
Long-Term debt	[1]	$ 639,271	$ 611,909

[1] Includes long-term debt due within one year. Excludes debt issuance costs and unamortized discount of $4.1 million and $4.5 million as of December 31, 2020 and 2019, respectively.