Fair Value of Financial Instruments (Details-1) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Carrying Amount [Member]
Assets:
Cash and cash equivalents	$ 88,719		$ 68,813
Liabilities:
Long-term debt	400,724	[1]	403,793	[1]
Fair Value [Member]
Assets:
Cash and cash equivalents	88,719		68,813
Liabilities:
Long-term debt	443,203	[1]	432,010	[1]
MGE [Member] | Carrying Amount [Member]
Assets:
Cash and cash equivalents	22,983		14,808
Liabilities:
Long-term debt	400,724	[1]	403,793	[1]
MGE [Member] | Fair Value [Member]
Assets:
Cash and cash equivalents	22,983		14,808
Liabilities:
Long-term debt	$ 443,203	[1]	$ 432,010	[1]

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