2.4.0.8040120 - Disclosure - Fair Value of Financial Instruments (Details-1)truefalseIn Thousands, unless otherwise specifiedfalse1false falsefalseFROM_Jan01_2013_TO_Jun30_2013http://www.sec.gov/CIK0001161728duration2013-01-01T00:00:002013-06-30T00:00:00PureStandardhttp://www.xbrl.org/2003/instancepurexbrli02false truefalseFROM_Jan01_2013_TO_Jun30_2013_us-gaap_RangeAxis_MaximumMemberhttp://www.sec.gov/CIK0001161728duration2013-01-01T00:00:002013-06-30T00:00:00falsefalseMaximum [Member]us-gaap_RangeAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_MaximumMemberus-gaap_RangeAxisexplicitMemberPureStandardhttp://www.xbrl.org/2003/instancepurexbrli03false truefalseFROM_Jan01_2013_TO_Jun30_2013_us-gaap_RangeAxis_MinimumMemberhttp://www.sec.gov/CIK0001161728duration2013-01-01T00:00:002013-06-30T00:00:00falsefalseMinimum [Member]us-gaap_RangeAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_MinimumMemberus-gaap_RangeAxisexplicitMemberPureStandardhttp://www.xbrl.org/2003/instancepurexbrli04false USDtruefalse$AS_OF_Jun30_2013_us-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxis_CarryingReportedAmountFairValueDisclosureMemberhttp://www.sec.gov/CIK0001161728instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseCarrying Amount [Member]us-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_CarryingReportedAmountFairValueDisclosureMemberus-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$5false USDtruefalse$AS_OF_Dec31_2012_us-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxis_CarryingReportedAmountFairValueDisclosureMemberhttp://www.sec.gov/CIK0001161728instant2012-12-31T00:00:000001-01-01T00:00:00falsefalseCarrying Amount [Member]us-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_CarryingReportedAmountFairValueDisclosureMemberus-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$6false USDtruefalse$AS_OF_Jun30_2013_us-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxis_EstimateOfFairValueFairValueDisclosureMemberhttp://www.sec.gov/CIK0001161728instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseFair Value [Member]us-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_EstimateOfFairValueFairValueDisclosureMemberus-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$7false USDtruefalse$AS_OF_Dec31_2012_us-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxis_EstimateOfFairValueFairValueDisclosureMemberhttp://www.sec.gov/CIK0001161728instant2012-12-31T00:00:000001-01-01T00:00:00falsefalseFair Value [Member]us-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_EstimateOfFairValueFairValueDisclosureMemberus-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$8false USDtruefalse$AS_OF_Jun30_2013_dei_LegalEntityAxis_SubsidiariesMember_us-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxis_CarryingReportedAmountFairValueDisclosureMemberhttp://www.sec.gov/CIK0001161728instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseMGE [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_SubsidiariesMemberdei_LegalEntityAxisexplicitMemberfalsefalseCarrying Amount [Member]us-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_CarryingReportedAmountFairValueDisclosureMemberus-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$9false USDtruefalse$AS_OF_Dec31_2012_dei_LegalEntityAxis_SubsidiariesMember_us-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxis_CarryingReportedAmountFairValueDisclosureMemberhttp://www.sec.gov/CIK0001161728instant2012-12-31T00:00:000001-01-01T00:00:00falsefalseMGE [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_SubsidiariesMemberdei_LegalEntityAxisexplicitMemberfalsefalseCarrying Amount [Member]us-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_CarryingReportedAmountFairValueDisclosureMemberus-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$10false USDtruefalse$AS_OF_Jun30_2013_dei_LegalEntityAxis_SubsidiariesMember_us-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxis_EstimateOfFairValueFairValueDisclosureMemberhttp://www.sec.gov/CIK0001161728instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseMGE [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_SubsidiariesMemberdei_LegalEntityAxisexplicitMemberfalsefalseFair Value [Member]us-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_EstimateOfFairValueFairValueDisclosureMemberus-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$11false USDtruefalse$AS_OF_Dec31_2012_dei_LegalEntityAxis_SubsidiariesMember_us-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxis_EstimateOfFairValueFairValueDisclosureMemberhttp://www.sec.gov/CIK0001161728instant2012-12-31T00:00:000001-01-01T00:00:00falsefalseMGE [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_SubsidiariesMemberdei_LegalEntityAxisexplicitMemberfalsefalseFair Value [Member]us-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_EstimateOfFairValueFairValueDisclosureMemberus-gaap_FairValueByBalanceSheetGroupingDisclosureItemAmountsAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$1true 4us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse6falsefalsefalse00falsefalsefalse7falsefalsefalse00falsefalsefalse8falsefalsefalse00falsefalsefalse9falsefalsefalse00falsefalsefalse10falsefalsefalse00falsefalsefalse11falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Assets:2false 5us-gaap_CashAndCashEquivalentsFairValueDisclosureus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4truefalsefalse4233300042333USD$falsetruefalse5truefalsefalse4635700046357USD$falsetruefalse6truefalsefalse4233300042333USD$falsetruefalse7truefalsefalse4635700046357USD$falsetruefalse8truefalsefalse53100005310USD$falsetruefalse9truefalsefalse63500006350USD$falsetruefalse10truefalsefalse53100005310USD$falsetruefalse11truefalsefalse63500006350USD$falsetruefalsexbrli:monetaryItemTypemonetaryThis element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 7 -Footnote 1 -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 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 8 -Footnote 2 -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 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 7, 8, 9, 10 -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. false2Cash and cash equivalents3true 4us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse6falsefalsefalse00falsefalsefalse7falsefalsefalse00falsefalsefalse8falsefalsefalse00falsefalsefalse9falsefalsefalse00falsefalsefalse10falsefalsefalse00falsefalsefalse11falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Liabilities:4false 5mgee_ShortTermDebtCommercialPaperFairValueDisclosuremgee_falsecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4truefalsefalse1400000014000falsefalsefalse5truefalsefalse00falsefalsefalse6truefalsefalse1400000014000falsefalsefalse7truefalsefalse00falsefalsefalse8truefalsefalse1400000014000falsefalsefalse9truefalsefalse00falsefalsefalse10truefalsefalse1400000014000falsefalsefalse11truefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThis element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents short-term debt commercial paper obligations meeting the definition of a liability which should be reported as of the balance sheet date.No definition available.false2Short-term debt - commercial paper5false 5mgee_LongTermDebtFairValueDisclosuremgee_falsecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4truefalsefalse360472000360472USD$falsetruefalse5truefalsefalse361805000361805USD$falsetruefalse6truefalsefalse401854000401854USD$falsetruefalse7truefalsefalse427456000427456USD$falsetruefalse8truefalsefalse360472000360472USD$falsetruefalse9truefalsefalse361805000361805USD$falsetruefalse10truefalsefalse401854000401854USD$falsetruefalse11truefalsefalse427456000427456USD$falsetruefalsexbrli:monetaryItemTypemonetaryThis element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents long-term debt obligations meeting the definition of a liability which should be reported as of the balance sheet date.No definition available.false2Long-term debt6true 3us-gaap_FairValueInputsAssetsQuantitativeInformationLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse6falsefalsefalse00falsefalsefalse7falsefalsefalse00falsefalsefalse8falsefalsefalse00falsefalsefalse9falsefalsefalse00falsefalsefalse10falsefalsefalse00falsefalsefalse11falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Fair Value Inputs Assets Quantitative Information [Line Items]7false 4mgee_FairValueInputsDeliveryPointsBasisAdjustmentOnPeakmgee_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse0.9630.963falsefalsefalse2falsetruefalse00falsefalsefalse3falsetruefalse00falsefalsefalse4falsetruefalse00falsefalsefalse5falsetruefalse00falsefalsefalse6falsetruefalse00falsefalsefalse7falsetruefalse00falsefalsefalse8falsetruefalse00falsefalsefalse9falsetruefalse00falsefalsefalse10falsetruefalse00falsefalsefalse11falsetruefalse00falsefalsefalsenum:percentItemTypepureBasis adjustment between delivery points for on peak electric future prices. Used as an input to measure fair value.No definition available.false0Basis adjustment - on peak8false 4mgee_FairValueInputsDeliveryPointsBasisAdjustmentOffPeakmgee_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse0.9570.957falsefalsefalse2falsetruefalse00falsefalsefalse3falsetruefalse00falsefalsefalse4falsetruefalse00falsefalsefalse5falsetruefalse00falsefalsefalse6falsetruefalse00falsefalsefalse7falsetruefalse00falsefalsefalse8falsetruefalse00falsefalsefalse9falsetruefalse00falsefalsefalse10falsetruefalse00falsefalsefalse11falsetruefalse00falsefalsefalsenum:percentItemTypepureBasis adjustment between delivery points for off peak electric future prices. Used as an input to measure fair value.No definition available.false0Basis adjustment - off peak9true 4mgee_FairValueInputsCounterpartyFuelMixAbstractmgee_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse6falsefalsefalse00falsefalsefalse7falsefalsefalse00falsefalsefalse8falsefalsefalse00falsefalsefalse9falsefalsefalse00falsefalsefalse10falsefalsefalse00falsefalsefalse11falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Counterparty fuel mix [Abstract]10false 5mgee_FairValueInputsCounterpartyFuelMixInternalGenerationmgee_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsetruefalse00falsefalsefalse2truetruefalse0.700.70falsefalsefalse3truetruefalse0.500.50falsefalsefalse4falsetruefalse00falsefalsefalse5falsetruefalse00falsefalsefalse6falsetruefalse00falsefalsefalse7falsetruefalse00falsefalsefalse8falsetruefalse00falsefalsefalse9falsetruefalse00falsefalsefalse10falsetruefalse00falsefalsefalse11falsetruefalse00falsefalsefalsenum:percentItemTypepureEstimate of counterparty's internal generation as a portion of their fuel mix, used as an input to measure fair value.No definition available.false0Internal generation11false 5mgee_FairValueInputsCounterpartyFuelMixPurchasedPowermgee_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsetruefalse00falsefalsefalse2truetruefalse0.500.50falsefalsefalse3truetruefalse0.300.30falsefalsefalse4falsetruefalse00falsefalsefalse5falsetruefalse00falsefalsefalse6falsetruefalse00falsefalsefalse7falsetruefalse00falsefalsefalse8falsetruefalse00falsefalsefalse9falsetruefalse00falsefalsefalse10falsetruefalse00falsefalsefalse11falsetruefalse00falsefalsefalsenum:percentItemTypepureEstimate of counterparty's purchased power as a portion of their fuel mix, used as an input to measure fair value.No definition available.false0Purchased powerfalseFair Value of Financial Instruments (Details-1) (USD $)ThousandsUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.mgeenergy.com/role/DisclosureFairValueOfFinancialInstrumentsDetails11111