Fair Value of Financial Instruments (Details-1) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Fair Value Measurement [Domain]
Liabilities:
Unamortized discount and debt issuance costs, net		$ 4,000	$ 4,100
Carrying Amount [Member]
Assets:
Cash and cash equivalents		102,916	95,959
Liabilities:
Long-term debt	[1]	399,074	391,242
Fair Value [Member]
Assets:
Cash and cash equivalents		102,916	95,959
Liabilities:
Long-term debt	[1]	450,497	430,122
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		5,831	10,768
Liabilities:
Long-term debt	[1]	399,074	391,242
MGE [Member] | Fair Value [Member]
Assets:
Cash and cash equivalents		5,831	10,768
Liabilities:
Long-term debt	[1]	$ 450,497	$ 430,122

[1] Includes long-term debt due within one year. Excludes debt issuance costs and unamortized discount of $4.0 million and $4.1 million at June 30, 2017, and December 31, 2016, respectively.