2.4.0.8010130 - Disclosure - Taxestruefalsefalse1false falsefalseFROM_Jan01_2013_TO_Jun30_2013http://www.sec.gov/CIK0001161728duration2013-01-01T00:00:002013-06-30T00:00:001true 1mgee_TaxesDisclosureAbstractmgee_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Taxes Disclosure [Abstract]2false 2us-gaap_IncomeTaxDisclosureTextBlockus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse005.       Taxes - MGE Energy and MGE. a.       Accounting for Uncertainty in Income Taxes. MGE Energy and MGE account for the difference between the tax benefit amount taken on prior year tax returns, or expected to be taken on a current year tax return, and the tax benefit amount recognized in the financial statements as an unrecognized tax benefit.  MGE Energy has adopted a tax method of accounting to accelerate tax deductions for repairs. MGE Energy and MGE have an unrecognized tax benefit at June 30, 2013 and December 31, 2012, in the amount of $1.9 million and $3.2 million, respectively, for the tax uncertainty related to the change in tax method of accounting for repairs. The reduction in unrecognized tax benefits is due to the Internal Revenue Service completing the examination of tax periods 2007-2009 with no adverse adjustments to these positions.b.       Effective Tax Rate. MGE Energy's and MGE's effective income tax rate for the three and six months ended June 30, 2013, are 38.4% and 38.0%, respectively, compared to 37.6% and 37.8% for the same periods in 2012.falsefalsefalsenonnum:textBlockItemTypenaThe entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)) -URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Article 4 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32537-109319 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32559-109319 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 109 -Paragraph 136, 172 -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 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 109 -Paragraph 43, 44, 45, 46, 47, 48, 49 -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. false0TaxesfalseTaxesUnKnownUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.mgeenergy.com/role/DisclosureTaxes12