Fair Value of Financial Instruments (Details-1) - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015
Liabilities:
Unamortized discount and debt issuance costs, net		$ 4,118	$ 4,498
Carrying Amount [Member]
Assets:
Cash and cash equivalents		95,959	81,384
Liabilities:
Long-Term debt	[1]	391,242	395,508
Fair Value [Member]
Assets:
Cash and cash equivalents		95,959	81,384
Liabilities:
Long-Term debt	[1]	430,122	435,767
MGE [Member]
Liabilities:
Unamortized discount and debt issuance costs, net		4,118	4,498
MGE [Member] | Carrying Amount [Member]
Assets:
Cash and cash equivalents		10,768	26,760
Liabilities:
Long-Term debt	[1]	391,242	395,508
MGE [Member] | Fair Value [Member]
Assets:
Cash and cash equivalents		10,768	26,760
Liabilities:
Long-Term debt	[1]	$ 430,122	$ 435,767

[1] Includes long-term debt due within one year. Excludes debt issuance costs and unamortized discount of $4.1 million and $4.5 million at December 31, 2016 and 2015, respectively.