Fair Value of Financial Instruments (Details-1) - USD ($) $ in Thousands		Mar. 31, 2016	Dec. 31, 2015
Carrying Amount [Member]
Assets:
Cash and cash equivalents		$ 97,331	$ 81,384
Liabilities:
Long-term debt	[1]	394,450	395,508
Fair Value [Member]
Assets:
Cash and cash equivalents		97,331	81,384
Liabilities:
Long-term debt	[1]	459,213	435,767
MGE [Member] | Carrying Amount [Member]
Assets:
Cash and cash equivalents		36,809	26,760
Liabilities:
Long-term debt	[1]	394,450	395,508
MGE [Member] | Fair Value [Member]
Assets:
Cash and cash equivalents		36,809	26,760
Liabilities:
Long-term debt	[1]	$ 459,213	$ 435,767

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