Fair Value of Financial Instruments (Details-2) (USD $)	6 Months Ended
	Jun. 30, 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	$ 422,000	$ 350,000
Total Assets	422,000	350,000
Liabilities:
Derivatives, net	79,362,000	42,356,000
Deferred compensation	1,856,000	1,725,000
Total liabilities	81,218,000	44,081,000
Derivative collateral	700,000	3,000,000
Level 1 [Member]
Assets:
Exchange-traded investments	422,000	350,000
Total Assets	422,000	350,000
Liabilities:
Derivatives, net	(218,000)	1,695,000
Deferred compensation	0	0
Total liabilities	(218,000)	1,695,000
Level 2 [Member]
Assets:
Exchange-traded investments	0	0
Total Assets	0	0
Liabilities:
Derivatives, net	0	0
Deferred compensation	1,856,000	1,725,000
Total liabilities	1,856,000	1,725,000
Level 3 [Member]
Assets:
Exchange-traded investments	0	0
Total Assets	0	0
Liabilities:
Derivatives, net	79,580,000	40,661,000
Deferred compensation	0	0
Total liabilities	79,580,000	40,661,000
MGE [Member]
Assets:
Exchange-traded investments	150,000	188,000
Total Assets	150,000	188,000
Liabilities:
Derivatives, net	79,362,000	42,356,000
Deferred compensation	1,856,000	1,725,000
Total liabilities	81,218,000	44,081,000
Derivative collateral	700,000	3,000,000
MGE [Member] | Level 1 [Member]
Assets:
Exchange-traded investments	150,000	188,000
Total Assets	150,000	188,000
Liabilities:
Derivatives, net	(218,000)	1,695,000
Deferred compensation	0	0
Total liabilities	(218,000)	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	1,856,000	1,725,000
Total liabilities	1,856,000	1,725,000
MGE [Member] | Level 3 [Member]
Assets:
Exchange-traded investments	0	0
Total Assets	0	0
Liabilities:
Derivatives, net	79,580,000	40,661,000
Deferred compensation	0	0
Total liabilities	$ 79,580,000	$ 40,661,000