2.4.0.8040027 - Disclosure - Columbia Environmental Project Construction (Details)truefalsefalse1false falsefalseAS_OF_Dec31_2014http://www.sec.gov/CIK0001161728instant2014-12-31T00:00:000001-01-01T00:00:00PureStandardhttp://www.xbrl.org/2003/instancepurexbrli02false USDfalsefalse$AS_OF_Jun30_2013http://www.sec.gov/CIK0001161728instant2013-06-30T00:00:000001-01-01T00:00:00PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$3false USDfalsefalse$AS_OF_Dec31_2012http://www.sec.gov/CIK0001161728instant2012-12-31T00:00:000001-01-01T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$4false USDtruefalse$FROM_Apr01_2013_TO_Jun30_2013_mgee_ConstructionProjectAxis_ColumbiaEnvironmentalProjectMemberhttp://www.sec.gov/CIK0001161728duration2013-04-01T00:00:002013-06-30T00:00:00falsefalseColumbia Environmental Project 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[Member]mgee_ConstructionProjectAxisxbrldihttp://xbrl.org/2006/xbrldimgee_ColumbiaEnvironmentalProjectMembermgee_ConstructionProjectAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDUSD$7false USDtruefalse$FROM_Jan01_2012_TO_Jun30_2012_mgee_ConstructionProjectAxis_ColumbiaEnvironmentalProjectMemberhttp://www.sec.gov/CIK0001161728duration2012-01-01T00:00:002012-06-30T00:00:00falsefalseColumbia Environmental Project [Member]mgee_ConstructionProjectAxisxbrldihttp://xbrl.org/2006/xbrldimgee_ColumbiaEnvironmentalProjectMembermgee_ConstructionProjectAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDUSD$8false truefalseAS_OF_Jun30_2013_us-gaap_JointlyOwnedUtilityPlantAxis_ColumbiaUnitsMemberhttp://www.sec.gov/CIK0001161728instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseColumbia Units [Member]us-gaap_JointlyOwnedUtilityPlantAxisxbrldihttp://xbrl.org/2006/xbrldimgee_ColumbiaUnitsMemberus-gaap_JointlyOwnedUtilityPlantAxisexplicitMemberPureStandardhttp://www.xbrl.org/2003/instancepurexbrli01true 3us-gaap_JointlyOwnedUtilityPlantInterestsLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse6falsefalsefalse00falsefalsefalse7falsefalsefalse00falsefalsefalse8falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Jointly Owned Utility Plant Interests [Line Items]2false 4mgee_JointlyOwnedUtilityPlantFacilityShareOfMgeNetGeneratingCapabilitymgee_falsenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsetruefalse00falsefalsefalse2falsetruefalse00falsefalsefalse3falsetruefalse00falsefalsefalse4falsetruefalse00falsefalsefalse5falsetruefalse00falsefalsefalse6falsetruefalse00falsefalsefalse7falsetruefalse00falsefalsefalse8truetruefalse0.290.29falsefalsefalsenum:percentItemTypepureA jointly owned utility plant's share of MGE's net generating capability.No definition available.false0Columbia's share of MGE's net generating capability3false 4us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShareus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsetruefalse00falsefalsefalse2falsetruefalse00falsefalsefalse3falsetruefalse00falsefalsefalse4falsetruefalse00falsefalsefalse5falsetruefalse00falsefalsefalse6falsetruefalse00falsefalsefalse7falsetruefalse00falsefalsefalse8truetruefalse0.220.22falsefalsefalsenum:percentItemTypepureThe proportionate share of interest (percent) in a jointly owned utility plant.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 10.C) -URI http://asc.fasb.org/extlink&oid=6500719&loc=d3e659983-123033 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section C false0Ownership interest in jointly owned plant4false 4mgee_JointlyOwnedUtilityPlantProportionateOwnershipShareWplmgee_falsenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsetruefalse00falsefalsefalse2falsetruefalse00falsefalsefalse3falsetruefalse00falsefalsefalse4falsetruefalse00falsefalsefalse5falsetruefalse00falsefalsefalse6falsetruefalse00falsefalsefalse7falsetruefalse00falsefalsefalse8truetruefalse0.4620.462falsefalsefalsenum:percentItemTypepureWPL's proportionate share of interest (percent) in Columbia, a jointly owned utility plant.No definition available.false0WPL ownership interest of Columbia5false 4mgee_JointlyOwnedUtilityPlantProportionateOwnershipShareWpscmgee_falsenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsetruefalse00falsefalsefalse2falsetruefalse00falsefalsefalse3falsetruefalse00falsefalsefalse4falsetruefalse00falsefalsefalse5falsetruefalse00falsefalsefalse6falsetruefalse00falsefalsefalse7falsetruefalse00falsefalsefalse8truetruefalse0.3180.318falsefalsefalsenum:percentItemTypepureWPSC's proportionate share of interest (percent) in Columbia, a jointly owned utility plant.No definition available.false0WPSC ownership interest of Columbia6true 3mgee_ExpectedCapitalExpendituresLineItemsmgee_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse6falsefalsefalse00falsefalsefalse7falsefalsefalse00falsefalsefalse8falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Expected Capital Expenditures [Line Items]7false 4mgee_ExpectedCapitalExpendituresmgee_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse6truefalsefalse140000000140000000USD$falsetruefalse7falsefalsefalse00falsefalsefalse8falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryExpected capital expenditures to be incurred during construction of an asset.No definition available.false2MGE's total share of expected capital expenditures8false 4mgee_ExpectedCapitalExpendituresCurrentYearmgee_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse6truefalsefalse2900000029000000falsefalsefalse7falsefalsefalse00falsefalsefalse8falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryExpected capital expenditures to be incurred during construction of an asset in the current year.No definition available.false2MGE's share of expected capital expenditures current year9false 4mgee_ExpectedCapitalExpendituresNextYearmgee_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse6truefalsefalse1200000012000000falsefalsefalse7falsefalsefalse00falsefalsefalse8falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryExpected capital expenditures to be incurred during construction of an asset next year.No definition available.false2MGE's share of expected capital expenditures next year10false 4us-gaap_ConstructionInProgressGrossus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2truefalsefalse132750000132750000falsefalsefalse3truefalsefalse9841100098411000falsefalsefalse4truefalsefalse9890000098900000falsefalsefalse5falsefalsefalse00falsefalsefalse6truefalsefalse9890000098900000falsefalsefalse7falsefalsefalse00falsefalsefalse8falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryGross amount, at the balance sheet date, of long-lived assets under construction that include construction costs to date on capital projects that have not been completed and assets being constructed that are not ready to be placed into service.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 5 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 false2Total incurred costs to date11false 4mgee_ColumbiaEnvironmentalProjectCommitmentsmgee_falsecreditinstantfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4truefalsefalse3860000038600000falsefalsefalse5falsefalsefalse00falsefalsefalse6truefalsefalse3860000038600000falsefalsefalse7falsefalsefalse00falsefalsefalse8falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryCommitted Columbia environmental project commitments.No definition available.false2Columbia environmental project commitments12false 4mgee_CarryingCostOnPreConstructionCostmgee_falsenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse11falsefalsefalse2falsetruefalse00falsefalsefalse3falsetruefalse00falsefalsefalse4truetruefalse0.50.5falsefalsefalse5truetruefalse11falsefalsefalse6truetruefalse0.50.5falsefalsefalse7truetruefalse11falsefalsefalse8falsetruefalse00falsefalsefalsenum: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 rate13false 4us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquityus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4truefalsefalse600000600000USD$falsetruefalse5truefalsefalse200000200000USD$falsetruefalse6truefalsefalse11000001100000USD$falsetruefalse7truefalsefalse300000300000USD$falsetruefalse8falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThe component of the allowance for funds used during construction during the period based on an assumed rate of return on equity funds used in financing the construction of regulated assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501569&loc=d3e55921-110430 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 71 -Paragraph 15 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501662&loc=d3e56162-110433 false2AFUDC - equity funds14false 4mgee_PublicUtilitiesPercentRateOfReturnmgee_falsenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsetruefalse00falsefalsefalse2truetruefalse0.50.5falsefalsefalse3falsetruefalse00falsefalsefalse4falsetruefalse00falsefalsefalse5falsetruefalse00falsefalsefalse6falsetruefalse00falsefalsefalse7falsetruefalse00falsefalsefalse8falsetruefalse00falsefalsefalsenum:percentItemTypepureRate MGE is entitled to earn a return on construction work in progress as approved in the current rate case for the year.No definition available.false0MGE rate of returnfalseColumbia Environmental Project Construction (Details) (USD $)NoRoundingUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.mgeenergy.com/role/DisclosureColumbiaEnvironmentalProjectConstructionDetails814