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25. REGULATORY CHARGES (Details) - BRL (R$) R$ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Liabilities
Energy Development Account (CDE)	R$ 58	R$ 122
Regulator inspection fee - ANEEL	3	2
Energy Efficiency Program	255	258
Research and development (R&D)	199	225
Energy System Expansion Research	3	2
National Scientific and Technological Development Fund	6	5
Proinfa - Alternative Energy Program	8	7
Royalties for use of water resources	10	6
Emergency capacity charge	26	31
Others	5	6
Liability	604	693
Current liabilities	457	514
Non-current liabilities	147	179
Regulatory Assets [member]
Liabilities
Global Reversion Reserve (RGR)	R$ 31	R$ 29

X

- Definition

Aneel inspection charge.

+ References

No definition available.

+ Details

Name:	cig_AneelInspectionCharge
Namespace Prefix:	cig_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Current regulatory liability.

+ References

No definition available.

+ Details

Name:	cig_CurrentRegulatoryLiability
Namespace Prefix:	cig_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Emergency capacity charge.

+ References

No definition available.

+ Details

Name:	cig_EmergencyCapacityCharge
Namespace Prefix:	cig_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Energy development account.

+ References

No definition available.

+ Details

Name:	cig_EnergyDevelopmentAccount
Namespace Prefix:	cig_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Energy efficiency program.

+ References

No definition available.

+ Details

Name:	cig_EnergyEfficiencyProgram
Namespace Prefix:	cig_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Energy system expansion research.

+ References

No definition available.

+ Details

Name:	cig_EnergySystemExpansionResearch
Namespace Prefix:	cig_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Global reversion reserve.

+ References

No definition available.

+ Details

Name:	cig_GlobalReversionReserve
Namespace Prefix:	cig_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

National scientific and technological development fund.

+ References

No definition available.

+ Details

Name:	cig_NationalScientificAndTechnologicalDevelopmentFund
Namespace Prefix:	cig_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Noncurrent regulatory liability.

+ References

No definition available.

+ Details

Name:	cig_NoncurrentRegulatoryLiability
Namespace Prefix:	cig_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Other current regulatory liability.

+ References

No definition available.

+ Details

Name:	cig_OtherCurrentRegulatoryLiability
Namespace Prefix:	cig_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Proinfa alternative energy program.

+ References

No definition available.

+ Details

Name:	cig_ProinfaAlternativeEnergyProgram
Namespace Prefix:	cig_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Royalties for use of water resources.

+ References

No definition available.

+ Details

Name:	cig_RoyaltiesForUseOfWaterResources
Namespace Prefix:	cig_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

The amount of regulatory deferral account credit balances and the related deferred tax liability. [Refer: Regulatory deferral account credit balances; Deferred tax liability associated with regulatory deferral account balances]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 14
-IssueDate 2019-01-01
-Paragraph 24
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=14&code=ifrs-tx-2019-en-r&anchor=para_24&doctype=Standard
-URIDate 2019-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 14
-IssueDate 2019-01-01
-Paragraph B11
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=14&code=ifrs-tx-2019-en-r&anchor=para_B11_a&doctype=Appendix&subtype=B
-URIDate 2019-03-27

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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- References

No definition available.

+ Details

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The amount of expenditure directly attributable to research or development activities, recognised in profit or loss.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 38
-IssueDate 2019-01-01
-Paragraph 126
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=38&code=ifrs-tx-2019-en-r&anchor=para_126&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_ResearchAndDevelopmentExpense
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: