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Valuation and Qualifying Accounts | 12 Months Ended
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Dec. 31, 2025
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract] |
SEC Schedule, 12-09, Schedule of Valuation and Qualifying Accounts Disclosure [Text Block] | Schedule II MGE Energy, Inc. and Madison Gas and Electric Company Valuation and Qualifying Accounts
|  |  |  |  | Additions |  |  |  |  |  |  |
|  | Balance at Beginning of Period |  |  | Charged to Costs and Expenses(b) |  |  | Charged to Other Accounts |  |  | Net Accounts Written Off(a) |  |  | Balance at End of Period |
Year ended 2023: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accumulated provision for uncollectibles |  | $ | 8,372,840 |  |  |  | 3,264,309 |  |  |  | 20,400 |  |  |  | (3,559,473 | ) |  | $ | 8,098,076 |
Year ended 2024: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accumulated provision for uncollectibles |  | $ | 8,098,076 |  |  |  | 4,850,000 |  |  |  | 54,000 |  |  |  | (3,972,334 | ) |  | $ | 9,029,742 |
Year ended 2025: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accumulated provision for uncollectibles |  | $ | 9,029,742 |  |  |  | 5,850,001 |  |  |  | 51,600 |  |  |  | (4,269,143 | ) |  | $ | 10,662,201 |
(a) Net of recovery of amounts previously written off. (b) For both the years ended December 31, 2025 and 2024, MGE recovered $4.9 million of bad debt expense as a regulatory asset. For the years ended December 31, 2025, 2024, and 2023, MGE deferred $1.9 million, $0.4 million, and $1.5 million, respectively, of bad debt expense as a regulatory asset. See Footnote 8 of the Notes to Consolidated Financial Statements in this Report for further information.

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- Definition The entire disclosure for valuation and qualifying accounts and reserves. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-X (SX) -Number 210 -Section 12 -Subsection 09 -Publisher SEC Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section S50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480738/235-10-S50-5 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 4 -Subparagraph (SX 210.12-09) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480678/235-10-S99-4 + Details
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