Fair Value of Financial Instruments (Details-1) - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020
Fair Value Measurement [Domain]
Liabilities:
Unamortized discount and debt issuance costs, net		$ 4,000	$ 4,100
Carrying Amount [Member]
Assets:
Cash and cash equivalents		40,239	44,738
Liabilities:
Short-term debt - commercial paper		54,000	52,500
Long-term debt	[1]	527,038	528,220
Fair Value [Member]
Assets:
Cash and cash equivalents		40,239	44,738
Liabilities:
Short-term debt - commercial paper		54,000	52,500
Long-term debt	[1]	590,748	639,271
MGE [Member] | Fair Value Measurement [Domain]
Liabilities:
Unamortized discount and debt issuance costs, net		4,000	4,100
MGE [Member] | Carrying Amount [Member]
Assets:
Cash and cash equivalents		6,709	4,103
Liabilities:
Short-term debt - commercial paper		54,000	52,500
Long-term debt	[1]	527,038	528,220
MGE [Member] | Fair Value [Member]
Assets:
Cash and cash equivalents		6,709	4,103
Liabilities:
Short-term debt - commercial paper		54,000	52,500
Long-term debt	[1]	$ 590,748	$ 639,271

[1] Includes long-term debt due within one year. Excludes debt issuance costs and unamortized discount of $4.0 million and $4.1 million as of March 31, 2021, and December 31, 2020, respectively.