Subsequent Events	6 Months Ended
Jun. 30, 2011
Subsequent Events Disclosure [Abstract]
Subsequent Events	16. Subsequent Events - MGE Energy and MGE. a. ATC Capital Contribution. On July 29, 2011, MGE Transco made a voluntary $0.3 million capital contribution to ATC. b. Credit Facilities On August 1, 2011, each of MGE Energy and MGE entered into an amendment to its existing credit agreement dated as of July 30, 2010, with various financial institutions and JPMorgan Chase Bank, N.A., as administrative agent. The existing credit agreements provide MGE Energy with a $40 million revolving credit facility and MGE with a $75 million revolving credit facility. The principal purpose of the amendments was to extend the termination date of the credit agreements by two years to July 31, 2015. The amendments also lowered the commitment fees, letter of credit fees and interest rate adders under the credit agreements. Borrowings under each credit agreement may bear interest at a rate that floats daily based upon a prime rate, or at a rate fixed for a specified interest period based upon a LIBOR-based index, in each case plus an adder based upon the senior unsecured credit rating for MGE. Based upon MGE's current senior unsecured credit rating, the adder is zero for prime rate-based borrowings and 0.850% for LIBOR-based borrowings. Each of MGE Energy and MGE paid an amendment fee in an amount equal to 0.075% of the total commitment under their respective credit agreements.

- 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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