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8. RECEIVABLES FROM CUSTOMERS, TRADERS AND POWER TRANSPORT CONCESSION HOLDERS (Details 3) - BRL (R$) R$ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018
Disclosure Of Advances From Customers [line items] |  |
Beginning balance | R$ 79 |
Ending Balance |  | R$ 79
Cemig GT [Member] |  |
Disclosure Of Advances From Customers [line items] |  |
Beginning balance |  | 233
Additions |  | 50
Energy supplied |  | (215)
Inflation adjustment |  | 11
Eletrobras [Member] |  |
Disclosure Of Advances From Customers [line items] |  |
Beginning balance | 79 |
Energy supplied | (80) |
Inflation adjustment | 1 |
Ending Balance |  | R$ 79

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- Definition Additions to advances payable. + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Disclosure Of Advances From Customers [line items] + References No definition available. + Details
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Namespace Prefix: | cig_
Data Type: | xbrli:stringItemType
Balance Type: | na
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- Definition Inflation adjustment on advance payable. + References No definition available. + Details
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Balance Type: | credit
Period Type: | duration

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- Definition Supply of energy disposals. + References No definition available. + Details
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Namespace Prefix: | cig_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition The amount of current payments received for goods or services to be provided in the future. [Refer: Advances received] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2019-01-01 -Paragraph 55 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_55&doctype=Standard -URIDate 2019-03-27 + Details
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Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Details
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Namespace Prefix: |
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Balance Type: |
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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |