Fair Value of Financial Instruments (Details-1) - USD ($) $ in Thousands		Jun. 30, 2016	Dec. 31, 2015
Carrying Amount [Member]
Assets:
Cash and cash equivalents		$ 110,308	$ 81,384
Liabilities:
Long-term debt	[1]	393,386	395,508
Fair Value [Member]
Assets:
Cash and cash equivalents		110,308	81,384
Liabilities:
Long-term debt	[1]	472,696	435,767
MGE [Member] | Carrying Amount [Member]
Assets:
Cash and cash equivalents		40,947	26,760
Liabilities:
Long-term debt	[1]	393,386	395,508
MGE [Member] | Fair Value [Member]
Assets:
Cash and cash equivalents		40,947	26,760
Liabilities:
Long-term debt	[1]	$ 472,696	$ 435,767

[1] *Includes long-term debt due within one year.