Fair Value of Financial Instruments (Details-1) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Carrying Amount [Member]
Assets:
Cash and cash equivalents	$ 70,703		$ 65,755
Liabilities:
Short-term debt - commercial paper	0		7,000
Long-term debt	398,653	[1]	399,690	[1]
Fair Value [Member]
Assets:
Cash and cash equivalents	70,703		65,755
Liabilities:
Short-term debt - commercial paper	0		7,000
Long-term debt	465,534	[1]	457,420	[1]
MGE [Member] | Carrying Amount [Member]
Assets:
Cash and cash equivalents	17,156		4,562
Liabilities:
Short-term debt - commercial paper	0		7,000
Long-term debt	398,653	[1]	399,690	[1]
MGE [Member] | Fair Value [Member]
Assets:
Cash and cash equivalents	17,156		4,562
Liabilities:
Short-term debt - commercial paper	0		7,000
Long-term debt	$ 465,534	[1]	$ 457,420	[1]

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