Fair Value of Financial Instruments (Details-1) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Carrying Amount [Member]
Assets:
Cash and cash equivalents	$ 65,755		$ 68,813
Liabilities:
Short-term debt - commercial paper	7,000		0
Long-Term debt	399,690	[1]	403,793	[1]
Fair Value [Member]
Assets:
Cash and cash equivalents	65,755		68,813
Liabilities:
Short-term debt - commercial paper	7,000		0
Long-Term debt	457,420	[1]	432,010	[1]
MGE [Member] | Carrying Amount [Member]
Assets:
Cash and cash equivalents	4,562		14,808
Liabilities:
Short-term debt - commercial paper	7,000		0
Long-Term debt	399,690	[1]	403,793	[1]
MGE [Member] | Fair Value [Member]
Assets:
Cash and cash equivalents	4,562		14,808
Liabilities:
Short-term debt - commercial paper	7,000		0
Long-Term debt	$ 457,420	[1]	$ 432,010	[1]

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