New Accounting Pronouncements	9 Months Ended
Sep. 30, 2012
New Accounting Pronouncements Disclosure [Abstract]
New Accounting Pronouncements	12. New Accounting Pronouncements - MGE Energy and MGE. a. Fair Value Measurements and Disclosures. In May 2011, the FASB issued authoritative guidance within the Codification's Fair Value Measurements and Disclosures topic that provides guidance on additional disclosures about fair value measurements, specifically related to Level 3 assets and liabilities. This authoritative guidance became effective January 1, 2012. The authoritative guidance did not have any financial impact, but required additional disclosures. See Footnote 11 for additional information. b. Presentation of Comprehensive Income. In June 2011, the FASB issued authoritative guidance within the Codification's Comprehensive Income topic that provides guidance on presentation of comprehensive income. Comprehensive income will be presented either in a single continuous statement of comprehensive income or in two separate but consecutive statements. This authoritative guidance became effective January 1, 2012. The authoritative guidance had an effect on our financial statement presentation of comprehensive income. See the Statement of Comprehensive Income for additional information. c. Disclosures about Offsetting Assets and Liabilities. In December 2011, the FASB issued authoritative guidance within the Codification's Balance Sheet topic that provides guidance on disclosures about offsetting assets and liabilities. The new disclosure requirements mandate that entities disclose both gross and net information for instruments and transactions eligible for offset in the balance sheet as well as instruments and transactions subject to a master netting arrangement. In addition, the standard requires disclosure of collateral received and posted in connections with a master netting arrangement. This authoritative guidance will become effective January 1, 2013. The authoritative guidance will not have a financial impact, but will require additional disclosures.

New Accounting Pronouncements

9 Months Ended

Sep. 30, 2012

New Accounting Pronouncements Disclosure [Abstract]

12. New Accounting Pronouncements - MGE Energy and MGE.

a. Fair Value Measurements and Disclosures.

In May 2011, the FASB issued authoritative guidance within the Codification's Fair Value Measurements and Disclosures topic that provides guidance on additional disclosures about fair value measurements, specifically related to Level 3 assets and liabilities. This authoritative guidance became effective January 1, 2012. The authoritative guidance did not have any financial impact, but required additional disclosures. See Footnote 11 for additional information.

b. Presentation of Comprehensive Income.

In June 2011, the FASB issued authoritative guidance within the Codification's Comprehensive Income topic that provides guidance on presentation of comprehensive income. Comprehensive income will be presented either in a single continuous statement of comprehensive income or in two separate but consecutive statements. This authoritative guidance became effective January 1, 2012. The authoritative guidance had an effect on our financial statement presentation of comprehensive income. See the Statement of Comprehensive Income for additional information.

c. Disclosures about Offsetting Assets and Liabilities.

In December 2011, the FASB issued authoritative guidance within the Codification's Balance Sheet topic that provides guidance on disclosures about offsetting assets and liabilities. The new disclosure requirements mandate that entities disclose both gross and net information for instruments and transactions eligible for offset in the balance sheet as well as instruments and transactions subject to a master netting arrangement. In addition, the standard requires disclosure of collateral received and posted in connections with a master netting arrangement. This authoritative guidance will become effective January 1, 2013. The authoritative guidance will not have a financial impact, but will require additional disclosures.