Subsequent Events	3 Months Ended
Mar. 31, 2012
Subsequent Events Disclosure [Abstract]
Subsequent Events	14. Subsequent Events - MGE Energy and MGE. a. Long-term Debt. On April 2, 2012, MGE issued $28 million in principal amount of its 4.38% senior notes, due April 1, 2042. The Notes were issued pursuant to a Note Purchase Agreement. The Notes are unsecured and are not issued under, or governed by, MGE's Indenture dated as of September 1, 1998, which governs MGE's Medium-Term Notes. MGE used the net proceeds from the sale of the Notes, together with other available corporate funds, to repay and retire on April 3, 2012, its obligations under a Loan Agreement dated as of April 1, 2002 with the City of Madison, Wisconsin, under which MGE received the net proceeds from the issuance of $28 million aggregate principal amount of 5.875% Series 2002A, Industrial Development Revenue Bonds that were issued by the City of Madison for MGE's benefit. The 5.875% Series 2002A Bonds were redeemed and retired on April 3, 2012 at 100% of their principal amount plus accrued interest with the proceeds of that loan repayment. Any interest savings in 2012 will be deferred. b. Remarketing of 4.875% Series 2002B, Industrial Development Revenue Bonds. On April 2, 2012, $19.3 million of 4.875% Series 2002B, Industrial Development Revenue Bonds were remarketed at an interest rate of 3.45%. The net proceeds of the 4.875% Series 2002B Bonds were originally loaned to MGE pursuant to a Loan Agreement dated as of April 1, 2002 with the City of Madison, which issued the Series 2002B Bonds in 2002. MGE is responsible for the payment of principal, premium, if any, and interest on the Bonds. The 4.875% Series 2002B Bonds were originally issued bearing an interest rate of 4.875% per annum for a period that ended April 1, 2012, at which point the Bonds were subject to mandatory tender by their holders and remarketing. The Series 2002B Bonds were remarketed and will carry an interest rate of 3.45% per annum, which is payable semi-annually on April 1 and October 1, until their maturity on October 1, 2027. The Series 2002B Bonds are redeemable on or after April 1, 2017, at a redemption price equal to 100% of the principal amount of the Bonds to be redeemed, plus accrued interest to the redemption date. c. ATC Capital Contribution. On April 30, 2012, MGE Transco made a voluntary $0.5 million capital contribution to ATC.

Subsequent Events

3 Months Ended

Mar. 31, 2012

Subsequent Events Disclosure [Abstract]

14. Subsequent Events - MGE Energy and MGE.

a. Long-term Debt.

On April 2, 2012, MGE issued $28 million in principal amount of its 4.38% senior notes, due April 1, 2042. The Notes were issued pursuant to a Note Purchase Agreement. The Notes are unsecured and are not issued under, or governed by, MGE's Indenture dated as of September 1, 1998, which governs MGE's Medium-Term Notes. MGE used the net proceeds from the sale of the Notes, together with other available corporate funds, to repay and retire on April 3, 2012, its obligations under a Loan Agreement dated as of April 1, 2002 with the City of Madison, Wisconsin, under which MGE received the net proceeds from the issuance of $28 million aggregate principal amount of 5.875% Series 2002A, Industrial Development Revenue Bonds that were issued by the City of Madison for MGE's benefit. The 5.875% Series 2002A Bonds were redeemed and retired on April 3, 2012 at 100% of their principal amount plus accrued interest with the proceeds of that loan repayment. Any interest savings in 2012 will be deferred.

b. Remarketing of 4.875% Series 2002B, Industrial Development Revenue Bonds.

On April 2, 2012, $19.3 million of 4.875% Series 2002B, Industrial Development Revenue Bonds were remarketed at an interest rate of 3.45%. The net proceeds of the 4.875% Series 2002B Bonds were originally loaned to MGE pursuant to a Loan Agreement dated as of April 1, 2002 with the City of Madison, which issued the Series 2002B Bonds in 2002. MGE is responsible for the payment of principal, premium, if any, and interest on the Bonds. The 4.875% Series 2002B Bonds were originally issued bearing an interest rate of 4.875% per annum for a period that ended April 1, 2012, at which point the Bonds were subject to mandatory tender by their holders and remarketing. The Series 2002B Bonds were remarketed and will carry an interest rate of 3.45% per annum, which is payable semi-annually on April 1 and October 1, until their maturity on October 1, 2027. The Series 2002B Bonds are redeemable on or after April 1, 2017, at a redemption price equal to 100% of the principal amount of the Bonds to be redeemed, plus accrued interest to the redemption date.

c. ATC Capital Contribution.

On April 30, 2012, MGE Transco made a voluntary $0.5 million capital contribution to ATC.