XML 101 R80.htm IDEA: XBRL DOCUMENT
v3.25.4

Pension Plans and Other Postretirement Benefits (Details-4) - Concentration | 12 Months Ended |
--- | --- | ---
Dec. 31, 2025 | Dec. 31, 2024
Pension Benefits [Member] | Plan Assets [Member] | Product Concentration Risk [Member] |  |  |
Concentration of Credit Risk [Abstract] |  |  |
Concentration Risk, Percentage |  | 10.00% |
Concentration risk, number of significant concentrations |  | 0 |
Pension Benefits [Member] | Equity Securities [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Target Plan Asset Allocation | [1],[2] | 45.00% |
Actual Plan Asset Allocation | [1] | 48.00% | 56.00%
Pension Benefits [Member] | United States Equity Securities [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Target Plan Asset Allocation |  | 32.00% |
Pension Benefits [Member] | Non-United States Equity Securities [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Target Plan Asset Allocation |  | 13.00% |
Pension Benefits [Member] | Fixed Income Securities [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Target Plan Asset Allocation | [2] | 50.00% |
Actual Plan Asset Allocation |  | 47.00% | 38.00%
Pension Benefits [Member] | Real Estate [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Target Plan Asset Allocation | [2] | 5.00% |
Actual Plan Asset Allocation |  | 5.00% | 6.00%
Postretirement Benefits [Member] | Equity Securities [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Target Plan Asset Allocation | [3] | 63.00% |
Actual Plan Asset Allocation | [3] | 65.00% | 66.00%
Postretirement Benefits [Member] | United States Equity Securities [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Target Plan Asset Allocation |  | 45.50% |
Postretirement Benefits [Member] | Non-United States Equity Securities [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Target Plan Asset Allocation |  | 17.50% |
Postretirement Benefits [Member] | Fixed Income Securities [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Target Plan Asset Allocation |  | 30.00% |
Actual Plan Asset Allocation |  | 29.00% | 28.00%
Postretirement Benefits [Member] | Real Estate [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Target Plan Asset Allocation |  | 7.00% |
Actual Plan Asset Allocation |  | 6.00% | 6.00%
[1] | Target allocations for equity securities are broken out as follows: 32% United States equity and 13% non-United States equity.
[2] | The target allocation for MGE's pension plans were approved to be rebalanced in December 2025. The trades happened in two steps, the first in December 2025 and the second in January 2026.
[3] | Target allocations for equity securities are broken out as follows: 45.5% United States equity and 17.5% non-United States equity.

X
- Definition When disclosing a particular concentration risk, the number of significant concentrations that exist as of the balance sheet date. + References No definition available. + Details
Name: | mgee_ConcentrationRiskNumberOfSignificantConcentrations
Namespace Prefix: | mgee_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 280 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 42 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482810/280-10-50-42 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 275 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 18 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482861/275-10-50-18 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 275 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482861/275-10-50-18 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 275 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 20 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482861/275-10-50-20 Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 275 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 18 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482861/275-10-50-18 Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 275 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 18 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482861/275-10-50-18 Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 275 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 18 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482861/275-10-50-18 + Details
Name: | us-gaap_ConcentrationRiskPercentage1
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_DefinedBenefitPlanInformationAboutPlanAssetsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480482/715-20-55-17 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
Name: | us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of actual investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
Name: | us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_RisksAndUncertaintiesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByBenchmarkAxis=mgee_PensionAndPostretirementBenefitPlanAssetsTotalMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByTypeAxis=us-gaap_ProductConcentrationRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=mgee_EquitySecuritiesDomesticMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=mgee_EquitySecuritiesForeignMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_FixedIncomeSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_RealEstateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |