Asset Retirement Obligations	9 Months Ended
Sep. 30, 2021
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligation	Asset Retirement Obligations - MGE Energy and MGE A liability is recorded for the fair value of an asset retirement obligation (ARO) to be recognized in the period in which it is incurred if it can be reasonably estimated. The offsetting associated asset retirement costs are capitalized as a long-lived asset and depreciated over the asset's useful life. As of September 30, 2021, MGE recorded an obligation of $3.9 million for the fair value of its legal liability for AROs associated with completed renewable projects and $3.5 million for the revision of its ARO legal liability with Columbia ash pond. MGE has regulatory treatment and recognizes regulatory assets or liabilities for the timing differences between when we recover legal AROs in rates and when those costs would actually be recognized.

The entire disclosure for an asset retirement obligation and the associated long-lived asset. An asset retirement obligation is a legal obligation associated with the disposal or retirement from service of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-URI http://asc.fasb.org/subtopic&trid=2175671

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