Fair Value of Financial Instruments (Details-1) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
Carrying Amount [Member]
Assets:
Cash and cash equivalents		$ 81,384	$ 65,755
Liabilities:
Short-term debt - commercial paper		0	7,000
Long-Term debt	[1]	395,508	399,690
Fair Value [Member]
Assets:
Cash and cash equivalents		81,384	65,755
Liabilities:
Short-term debt - commercial paper		0	7,000
Long-Term debt	[1]	435,767	457,420
MGE [Member] | Carrying Amount [Member]
Assets:
Cash and cash equivalents		26,760	4,562
Liabilities:
Short-term debt - commercial paper		0	7,000
Long-Term debt	[1]	395,508	399,690
MGE [Member] | Fair Value [Member]
Assets:
Cash and cash equivalents		26,760	4,562
Liabilities:
Short-term debt - commercial paper		0	7,000
Long-Term debt	[1]	$ 435,767	$ 457,420

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