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3. PRINCIPLES OF CONSOLIDATION (Details Narrative) |  | 12 Months Ended
--- | --- | ---
Jan. 13, 2020 | Dec. 31, 2020
Centroeste [member] |  |
Disclosure of subsidiaries [line items] |  |
Percentage of ownership interest in entities wholly owned directly or indirectly | 49.00% | 100.00%

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- Definition Percentage of ownership interest in entities wholly owned directly or indirectly. + References No definition available. + Details
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Namespace Prefix: | cig_
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Balance Type: | na
Period Type: | duration

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- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table. + References No definition available. + Details
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Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | ifrs-full_SignificantInvestmentsInSubsidiariesAxis=cig_CentroesteMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |