Fair Value of Financial Instruments (Details-2) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Assets:
Exchange-traded investments	$ 350,000	$ 430,000
Total Assets	350,000	430,000
Liabilities:
Derivatives, net	42,356,000	19,230,000
Deferred compensation	1,725,000	1,525,000
Total Liabilities	44,081,000	20,755,000
Derivative collateral	3,000,000	500,000
Deferred compensation interest calculation [Abstract]
U.S Treasury Bills maturity	26 Weeks
Increase compounded monthly	1.00%
Minimum annual rate	7.00%
Level 1 [Member]
Assets:
Exchange-traded investments	350,000	430,000
Total Assets	350,000	430,000
Liabilities:
Derivatives, net	1,695,000	14,000
Deferred compensation	0	1,525,000
Total Liabilities	1,695,000	1,539,000
Level 2 [Member]
Assets:
Exchange-traded investments	0	0
Total Assets	0	0
Liabilities:
Derivatives, net	0	0
Deferred compensation	1,725,000	0
Total Liabilities	1,725,000	0
Level 3 [Member]
Assets:
Exchange-traded investments	0	0
Total Assets	0	0
Liabilities:
Derivatives, net	40,661,000	19,216,000
Deferred compensation	0	0
Total Liabilities	40,661,000	19,216,000
MGE [Member]
Assets:
Exchange-traded investments	188,000	260,000
Total Assets	188,000	260,000
Liabilities:
Derivatives, net	42,356,000	19,230,000
Deferred compensation	1,725,000	1,525,000
Total Liabilities	44,081,000	20,755,000
Derivative collateral	3,000,000	500,000
MGE [Member] | Level 1 [Member]
Assets:
Exchange-traded investments	188,000	260,000
Total Assets	188,000	260,000
Liabilities:
Derivatives, net	1,695,000	14,000
Deferred compensation	0	1,525,000
Total Liabilities	1,695,000	1,539,000
MGE [Member] | Level 2 [Member]
Assets:
Exchange-traded investments	0	0
Total Assets	0	0
Liabilities:
Derivatives, net	0	0
Deferred compensation	1,725,000	0
Total Liabilities	1,725,000	0
MGE [Member] | Level 3 [Member]
Assets:
Exchange-traded investments	0	0
Total Assets	0	0
Liabilities:
Derivatives, net	40,661,000	19,216,000
Deferred compensation	0	0
Total Liabilities	$ 40,661,000	$ 19,216,000