Fair Value of Financial Instruments (Details-1) - USD ($) $ in Thousands		Dec. 31, 2019	Dec. 31, 2018
Liabilities:
Unamortized discount and debt issuance costs, net		$ 4,479	$ 4,535
Carrying Amount [Member]
Assets:
Cash and cash equivalents		23,481	83,102
Liabilities:
Short-term debt - commercial paper		0	13,000
Long-Term debt	[1]	547,879	502,431
Fair Value [Member]
Assets:
Cash and cash equivalents		23,481	83,102
Liabilities:
Short-term debt - commercial paper		0	13,000
Long-Term debt	[1]	611,909	518,811
MGE [Member] | Fair Value Disclosure Item Amounts [Domain]
Liabilities:
Unamortized discount and debt issuance costs, net		4,479	4,535
MGE [Member] | Carrying Amount [Member]
Assets:
Cash and cash equivalents		3,196	4,843
Liabilities:
Short-term debt - commercial paper		0	13,000
Long-Term debt	[1]	547,879	502,431
MGE [Member] | Fair Value [Member]
Assets:
Cash and cash equivalents		3,196	4,843
Liabilities:
Short-term debt - commercial paper		0	13,000
Long-Term debt	[1]	$ 611,909	$ 518,811

[1] (a) Includes long-term debt due within one year. Excludes debt issuance costs and unamortized discount of $4.5 million as of December 31, 2019 and 2018.