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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%

X

- Definition

Percentage of ownership interest in entities wholly owned directly or indirectly.

+ References

No definition available.

+ Details

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Namespace Prefix:	cig_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- 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

X

- Details

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