Rate Matters	12 Months Ended
Rate Matters	Dec. 31, 2015
Regulated Operations [Abstract]
Rate Matters	Rate Matters - MGE Energy and MGE. a. Rate Proceedings. In July 2015, the PSCW approved MGE's request to extend the current accounting treatment for transmission related costs through 2016, conditioned upon MGE not filing a base rate case for 2016. This accounting treatment will allow MGE to reflect any differential between transmission costs reflected in rates and actual costs incurred in its next rate case filing. On December 23, 2014, the PSCW authorized MGE to increase 2015 rates for retail electric customers by 3.8% or $15.4 million and to decrease gas rates by 2.0% or $3.8 million. The increase in retail electric rates cover costs associated with the construction of emission-reduction equipment at Columbia, improvements and reliability of the state's electric transmission system, fuel and purchased power related to coal delivery costs, partially offset by lower cost as a result of market conditions for pension and postretirement benefit costs. The authorized return on common stock equity is 10.2%. The PSCW also approved changes to customer rates and rate design for gas service that became effective January 1, 2015. Gas rate design consists of a fixed monthly customer charge and a variable charge tied to actual usage, in addition to the separate charge through the PGA for natural gas commodity costs. The change shifted more of the rate recovery to the monthly charge, reflecting the related fixed costs of providing gas services, and reduced the variable usage-based charge. Thus, gas net income is expected to be more evenly distributed during the year and less sensitive to weather. On July 26, 2013, the PSCW authorized MGE to freeze electric and natural gas rates at 2013 levels for 2014. The order authorized 100% AFUDC on the Columbia scrubber construction project and deferral of increased costs related to ATC and MISO network upgrade fees. As part of the rate freeze plan authorized by the PSCW, effective January 1, 2014, approximately $6.3 million associated with a 2012 fuel rule surplus credit was amortized in 2014. The fuel credit accrued interest at MGE's weighted cost of capital. The authorized return on common stock equity was unchanged at 10.3%. On December 14, 2012, the PSCW authorized MGE to increase 2013 rates for retail electric customers by 3.8% or $14.9 million and to increase gas rates by 1.0% or $1.6 million. The change in retail electric rates was driven by costs for new environmental equipment at Columbia, final construction costs for the Elm Road Units, transmission reliability enhancements, and purchased power costs. The authorized return on common stock equity remained unchanged at 10.3%. b. Fuel Rules. Fuel rules require the PSCW and Wisconsin utilities to defer electric fuel-related costs that fall outside a symmetrical cost tolerance band around the amount approved for a utility in its annual fuel proceedings. Any over/under recovery of the actual costs is determined on an annual basis and is adjusted in future billings to electric retail customers. The fuel rules bandwidth is currently set at plus or minus 2%. Under fuel rules, MGE would defer costs, less any excess revenues, if its actual electric fuel costs exceeded 102% of the electric fuel costs allowed in its latest rate order. Excess revenues are defined as revenues in the year in question that provide MGE with a greater return on common equity than authorized by the PSCW in MGE's latest rate order. Conversely, MGE is required to defer the benefit of lower costs if actual electric fuel costs were less than 98% of the electric fuel costs allowed in that order. In August 2015, the PSCW approved a $0.00256/kWh fuel credit to begin on September 1, 2015, and continue throughout 2016. The fuel credit established a mechanism to return fuel savings to electric customers as a bill credit. MGE returned $2.6 million of electric fuel-related savings in customer bill credits during the period from September 1, 2015, through December 31, 2015. As of December 31, 2015, MGE has deferred $9.5 million of 2015 electric fuel-related savings that are outside the range authorized by the PSCW. These costs are subject to PSCW's annual review, expected to be completed in 2016. In January 2016, the PSCW lowered MGE's 2016 fuel rules monitored costs by $14.8 million as a result of continued lower projected fuel costs in 2016. The PSCW will address the return of the 2016 fuel savings to customers as an update to the fuel credit or through another approved mechanism. The return of the fuel savings to customers for 2016 will be addressed during the PSCW's annual review during 2016 of 2015 fuel costs. MGE will defer these fuel savings until a determination is made by the PSCW. As part of the rate freeze plan authorized by the PSCW for 2014, $6.3 million associated with the 2012 fuel rule credit was amortized against purchased power expense during the year ended December 31, 2014. The 2013 fuel credit of $6.5 million was returned to customers in October 2014.