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20. INTANGIBLE ASSETS (Details Narrative) - BRL (R$) R$ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Disclosure of detailed information about intangible assets [abstract] |  |  |
Capitalized borrowing costs | R$ 2 | R$ 4 | R$ 71
Annual average amortization rate | 4.01% |  |

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- Definition Amount rfers to capitilized borrowing cost. + References No definition available. + Details
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Namespace Prefix: | cig_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Amount refers to useful lives or amortisation rates intangible assets other than goodwill. + References No definition available. + Details
Name: | cig_UsefulLivesOrAmortisationRatesIntangibleAssetsOtherThanGoodwill
Namespace Prefix: | cig_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
Name: | ifrs-full_DisclosureOfIntangibleAssetsAbstract
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration