Commitments and Contingencies (Details-1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 MW
Purchase Obligation, Fiscal Year Maturity [Abstract]
Purchase obligation due in next twelve months	122,841
Purchase obligation due in second year	78,534
Purchase obligation due in third year	63,703
Purchase obligation due in fourth year	57,828
Purchase obligation due in fifth year	41,360
Coal [Member]
Purchase Obligation, Fiscal Year Maturity [Abstract]
Purchase obligation due in next twelve months	22,630	[1]
Purchase obligation due in second year	16,436	[1]
Purchase obligation due in third year	10,664	[1]
Purchase obligation due in fourth year	6,560	[1]
Purchase obligation due in fifth year	3,850	[1]
Natural Gas, Transportation and Storage [Member]
Purchase Obligation, Fiscal Year Maturity [Abstract]
Purchase obligation due in next twelve months	18,074	[2]
Purchase obligation due in second year	9,938	[2]
Purchase obligation due in third year	273	[2]
Purchase obligation due in fourth year	192	[2]
Purchase obligation due in fifth year	0	[2]
Natural Gas, Supply [Member]
Purchase Obligation, Fiscal Year Maturity [Abstract]
Purchase obligation due in next twelve months	14,971	[3]
Purchase obligation due in second year	0	[3]
Purchase obligation due in third year	0	[3]
Purchase obligation due in fourth year	0	[3]
Purchase obligation due in fifth year	0	[3]
Purchase Power [Member]
Purchase Obligation, Fiscal Year Maturity [Abstract]
Purchase obligation due in next twelve months	50,714	[4]
Purchase obligation due in second year	51,437	[4]
Purchase obligation due in third year	52,043	[4]
Purchase obligation due in fourth year	50,752	[4]
Purchase obligation due in fifth year	37,367	[4]
Ten-year Purchase Power Agreement, Osceola Windpower II, LLC [Member]
Purchase Power Agreement [Abstract]
Long-term purchase commitment, term	10 years
Long-term purchase commitment, minimum power required (in MW)	50
Other [Member]
Purchase Obligation, Fiscal Year Maturity [Abstract]
Purchase obligation due in next twelve months	16,452
Purchase obligation due in second year	723
Purchase obligation due in third year	723
Purchase obligation due in fourth year	324
Purchase obligation due in fifth year	143

[1] Total coal commitments for the Columbia and Elm Road Units, including transportation. Fuel procurement for MGE's jointly owned Columbia and Elm Road Units are handled by WPL and WEPCO, respectively, who are the operators of those facilities. If any minimum purchase obligations must be paid under these contracts, management believes these obligations would be considered costs of service and recoverable in rates.

[2] MGE's natural gas transportation and storage contracts require fixed monthly payments for firm supply pipeline transportation and storage capacity. The pricing components of the fixed monthly payments for the transportation and storage contracts are established by FERC but may be subject to change.

[3] These commitments include market-based pricing. Management expects to recover these costs in future customer rates.

[4] MGE has several purchase power agreements to help meet future electric supply requirements. Management expects to recover these costs in future customer rates. In October 2008, MGE entered into a ten-year purchase power agreement to help meet future electric supply requirements. Under this agreement, MGE has agreed to purchase 50 MW of wind power from Osceola Windpower II, LLC, which is located in Iowa. This facility became operational in October 2008. MGE does not have any capacity payment commitments under this agreement. However, MGE is obligated to purchase its ratable share of the energy produced by the project. MGE's commitment related to its ratable share of energy produced by the project has been estimated and is included in the above numbers.