Fair Value of Financial Instruments (Details-1) - USD ($) $ in Thousands		Sep. 30, 2020	Dec. 31, 2019
Fair Value Measurement [Domain]
Liabilities:
Unamortized discount and debt issuance costs, net		$ 4,300	$ 4,500
Carrying Amount [Member]
Assets:
Cash and cash equivalents		53,058	23,481
Liabilities:
Long-term debt	[1]	544,395	547,879
Fair Value [Member]
Assets:
Cash and cash equivalents		53,058	23,481
Liabilities:
Long-term debt	[1]	658,008	611,909
MGE [Member] | Carrying Amount [Member]
Assets:
Cash and cash equivalents		5,171	3,196
Liabilities:
Long-term debt	[1]	544,395	547,879
MGE [Member] | Fair Value [Member]
Assets:
Cash and cash equivalents		5,171	3,196
Liabilities:
Long-term debt	[1]	$ 658,008	$ 611,909

[1] Includes long-term debt due within one year. Excludes debt issuance costs and unamortized discount of $4.3 million and $4.5 million as of September 30, 2020, and December 31, 2019, respectively.