2.4.0.8040110 - Disclosure - Rate Matters (Details)truefalseIn Millions, unless otherwise specifiedfalse1false USDfalsefalse$FROM_Jan01_2014_TO_Dec31_2014http://www.sec.gov/CIK0001161728duration2014-01-01T00:00:002014-12-31T00:00:00PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$2false USDfalsefalse$FROM_Jan01_2013_TO_Dec31_2013http://www.sec.gov/CIK0001161728duration2013-01-01T00:00:002013-12-31T00:00:00PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$3false USDfalsefalse$FROM_Jan01_2012_TO_Dec31_2012http://www.sec.gov/CIK0001161728duration2012-01-01T00:00:002012-12-31T00:00:00PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$4false USDfalsefalse$AS_OF_Jun30_2013http://www.sec.gov/CIK0001161728instant2013-06-30T00:00:000001-01-01T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$1true 2mgee_RateProceedingsAbstractmgee_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Rate Proceedings [Abstract]2false 3mgee_AuthorizedPercentIncreaseDecreaseElectricmgee_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse00falsefalsefalse2truetruefalse0.0380.038falsefalsefalse3truetruefalse0.0430.043falsefalsefalse4falsetruefalse00falsefalsefalsenum:percentItemTypepureAuthorized percentage rate increase (decrease) for retail electric customers.No definition available.false0Authorized percentage increase (decrease) for electric3false 3mgee_AuthorizedRateIncreaseDecreaseElectricmgee_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2truefalsefalse1490000014.9USD$falsetruefalse3truefalsefalse1570000015.7USD$falsetruefalse4falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryAuthorized rate increase (decrease) for retail electric customers.No definition available.false2Authorized rate increase (decrease) for electric4false 3mgee_AuthorizedPercentIncreaseDecreaseGasmgee_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse00falsefalsefalse2truetruefalse0.010.01falsefalsefalse3truetruefalse0.0030.003falsefalsefalse4falsetruefalse00falsefalsefalsenum:percentItemTypepureAuthorized percentage rate increase (decrease) for retail gas customers.No definition available.false0Authorized percentage increase (decrease) for gas5false 3mgee_AuthorizedRateIncreaseDecreaseGasmgee_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2truefalsefalse16000001.6falsefalsefalse3truefalsefalse6000000.6falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryAuthorized rate increase (decrease) for retail gas customers.No definition available.false2Authorized rate increase (decrease) for gas6false 3mgee_FuelRulesBandwidthmgee_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00falsefalsefalse2truetruefalse0.020.02falsefalsefalse3falsetruefalse00falsefalsefalse4falsetruefalse00falsefalsefalsenum:percentItemTypepurePursuant to the provisions of the rate order, the fuel rules bandwidth will be plus or minus this percentage.No definition available.false0Fuel rules bandwidth7false 3mgee_AuthorizedReturnOnCommonStockmgee_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.1030.103falsefalsefalse2truetruefalse0.1030.103falsefalsefalse3falsetruefalse00falsefalsefalse4falsetruefalse00falsefalsefalsenum:percentItemTypepureAuthorized return on common stock equity.No definition available.false0Authorized return on common stock8false 3mgee_CarryingCostOnPreConstructionCostmgee_falsenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse11falsefalsefalse2falsetruefalse00falsefalsefalse3falsetruefalse00falsefalsefalse4falsetruefalse00falsefalsefalsenum:percentItemTypepureRate MGE is entitled to a carrying cost on the related construction costs of the Columbia expenditures related to the construction of air emission reduction systems and associated equipment on Columbia Units 1 and 2.No definition available.false0Carrying cost on pre-construction costs - AFUDC rate9false 3mgee_ReturnElectricFuelCreditmgee_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse62000006.2falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryFuel rule surplus credit to be amortized. The fuel credit will accrue interest at MGE's weighted cost of capital.No definition available.false2Return of electric fuel credit10true 2mgee_FuelRulesAbstractmgee_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Fuel Rules [Abstract]11false 3mgee_ElectricFuelDeferredCostsUpperThresholdmgee_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00falsefalsefalse2truetruefalse1.021.02falsefalsefalse3falsetruefalse00falsefalsefalse4falsetruefalse00falsefalsefalsenum:percentItemTypepureUnder fuel rules, the amount in which MGE would defer if actual electric fuel costs exceeded allowed electric fuel costs in latest rate order.No definition available.false0Electric fuel deferred costs upper threshold12false 3mgee_ElectricFuelDeferredCostsLowerThresholdmgee_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00falsefalsefalse2truetruefalse0.980.98falsefalsefalse3falsetruefalse00falsefalsefalse4falsetruefalse00falsefalsefalsenum:percentItemTypepureUnder fuel rules, the amount in which MGE is required to defer the benefit of lower costs if actual electric fuel costs were less than the allowed electric fuel costs in latest rate order.No definition available.false0Electric fuel deferred costs lower threshold13false 3mgee_IncreasedElectricFuelCostsDeferredmgee_falsecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4truefalsefalse4000000.4USD$falsetruefalsexbrli:monetaryItemTypemonetaryThe amount of electric fuel-related costs in which MGE has deferred outside the 102% or 98% range authorized by the PSCW in the most recent rate order.No definition available.false2Increased (decreased) electric fuel costs deferredfalseRate Matters (Details) (USD $)HundredThousandsUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.mgeenergy.com/role/DisclosureRateMattersDetails413