Fair Value of Financial Instruments (Details-2) (USD $)	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
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	$ 428,000	$ 320,000
Total Assets	428,000	320,000
Liabilities:
Derivatives, net	69,197,000	72,329,000
Deferred compensation	2,085,000	2,010,000
Total liabilities	71,282,000	74,339,000
Derivative collateral	500,000	0
Level 1 [Member]
Assets:
Exchange-traded investments	428,000	320,000
Total Assets	428,000	320,000
Liabilities:
Derivatives, net	(401,000)	(17,000)
Deferred compensation	0	0
Total liabilities	(401,000)	(17,000)
Level 2 [Member]
Assets:
Exchange-traded investments	0	0
Total Assets	0	0
Liabilities:
Derivatives, net	0	0
Deferred compensation	2,085,000	2,010,000
Total liabilities	2,085,000	2,010,000
Level 3 [Member]
Assets:
Exchange-traded investments	0	0
Total Assets	0	0
Liabilities:
Derivatives, net	69,598,000	72,346,000
Deferred compensation	0	0
Total liabilities	69,598,000	72,346,000
MGE [Member]
Assets:
Exchange-traded investments	161,000	117,000
Total Assets	161,000	117,000
Liabilities:
Derivatives, net	69,197,000	72,329,000
Deferred compensation	2,085,000	2,010,000
Total liabilities	71,282,000	74,339,000
Derivative collateral	500,000	0
MGE [Member] | Level 1 [Member]
Assets:
Exchange-traded investments	161,000	117,000
Total Assets	161,000	117,000
Liabilities:
Derivatives, net	(401,000)	(17,000)
Deferred compensation	0	0
Total liabilities	(401,000)	(17,000)
MGE [Member] | Level 2 [Member]
Assets:
Exchange-traded investments	0	0
Total Assets	0	0
Liabilities:
Derivatives, net	0	0
Deferred compensation	2,085,000	2,010,000
Total liabilities	2,085,000	2,010,000
MGE [Member] | Level 3 [Member]
Assets:
Exchange-traded investments	0	0
Total Assets	0	0
Liabilities:
Derivatives, net	69,598,000	72,346,000
Deferred compensation	0	0
Total liabilities	$ 69,598,000	$ 72,346,000