Subsequent Events	12 Months Ended
Dec. 31, 2011
Subsequent Events Disclosure [Abstract]
Subsequent Events	26. Subsequent Events - MGE Energy and MGE. ATC Capital Contribution. On January 30, 2012, MGE Transco made a voluntary $0.4 million capital contribution to ATC.

- Definition

Tabular disclosure of significant events or transactions that occurred after the balance sheet date through the date the financial statements were issued or the date the financial statements were available to be issued. Examples include: the sale of a capital stock issue, purchase of a business, settlement of litigation, losses resulting from fire or flood, losses on receivables, significant realized and unrealized gains and losses that result from changes in quoted market prices of securities, declines in market prices of inventory, changes in authorized or issued debt (SEC), significant foreign exchange rate changes, substantial loans to insiders or affiliates, significant long-term investments, and substantial dividends not in the ordinary course of business.

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