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8. RECEIVABLES FROM CUSTOMERS, TRADERS AND POWER TRANSPORT CONCESSION HOLDERS (Details Narrative) - BRL (R$) R$ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 | Jun. 30, 2019
Disclosure Of Advances From Customers [line items] |  |
Debts |  | R$ 240
Impairment | R$ 210 |
Cemig Distribuicao SA [member] |  |
Disclosure Of Advances From Customers [line items] |  |
Reduction in doubtful accounts | R$ 46 |

X
- Definition Represent information about the debts. + References No definition available. + Details
Name: | cig_Debts
Namespace Prefix: | cig_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The amount of reduction in doubtful accounts. + References No definition available. + Details
Name: | cig_DecreaseInDoubtfulAccounts
Namespace Prefix: | cig_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Disclosure Of Advances From Customers [line items] + References No definition available. + Details
Name: | cig_DisclosureOfAdvancesFromCustomersLineItems
Namespace Prefix: | cig_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represent information about the impairment. + References No definition available. + Details
Name: | cig_Impairment
Namespace Prefix: | cig_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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