Fair Value of Financial Instruments (Details-2) (USD $)	3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
Deferred compensation interest calculation [Abstract]
U.S Treasury Bills maturity	26
Increase compounded monthly	1.00%
Minimum annual rate	7.00%
Assets:
Exchange-traded investments	$ 361,000	$ 350,000
Total Assets	361,000	350,000
Liabilities:
Derivatives, net	71,514,000	42,356,000
Deferred compensation	1,771,000	1,725,000
Total liabilities	73,285,000	44,081,000
Derivative collateral	2,000,000	3,000,000
Level 1 [Member]
Assets:
Exchange-traded investments	361,000	350,000
Total Assets	361,000	350,000
Liabilities:
Derivatives, net	326,000	1,695,000
Deferred compensation	0	0
Total liabilities	326,000	1,695,000
Level 2 [Member]
Assets:
Exchange-traded investments	0	0
Total Assets	0	0
Liabilities:
Derivatives, net	0	0
Deferred compensation	1,771,000	1,725,000
Total liabilities	1,771,000	1,725,000
Level 3 [Member]
Assets:
Exchange-traded investments	0	0
Total Assets	0	0
Liabilities:
Derivatives, net	71,188,000	40,661,000
Deferred compensation	0	0
Total liabilities	71,188,000	40,661,000
MGE [Member]
Assets:
Exchange-traded investments	162,000	188,000
Total Assets	162,000	188,000
Liabilities:
Derivatives, net	71,514,000	42,356,000
Deferred compensation	1,771,000	1,725,000
Total liabilities	73,285,000	44,081,000
Derivative collateral	2,000,000	3,000,000
MGE [Member] | Level 1 [Member]
Assets:
Exchange-traded investments	162,000	188,000
Total Assets	162,000	188,000
Liabilities:
Derivatives, net	326,000	1,695,000
Deferred compensation	0	0
Total liabilities	326,000	1,695,000
MGE [Member] | Level 2 [Member]
Assets:
Exchange-traded investments	0	0
Total Assets	0	0
Liabilities:
Derivatives, net	0	0
Deferred compensation	1,771,000	1,725,000
Total liabilities	1,771,000	1,725,000
MGE [Member] | Level 3 [Member]
Assets:
Exchange-traded investments	0	0
Total Assets	0	0
Liabilities:
Derivatives, net	71,188,000	40,661,000
Deferred compensation	0	0
Total liabilities	$ 71,188,000	$ 40,661,000