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17. PROPERTY, PLANT AND EQUIPMENT (Details 2) | 12 Months Ended
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Dec. 31, 2020
Reservoirs, dams and watercourses [member] | Generation unit [member] |
Disclosure of detailed information about property, plant and equipment [line items] |
Property plant and equipment depreciation rate | 2.00%
Buildings - machine room [member] | Generation unit [member] |
Disclosure of detailed information about property, plant and equipment [line items] |
Property plant and equipment depreciation rate | 2.00%
Buildings - other [member] | Generation unit [member] |
Disclosure of detailed information about property, plant and equipment [line items] |
Property plant and equipment depreciation rate | 3.33%
Buildings - other [member] | Administration unit [member] |
Disclosure of detailed information about property, plant and equipment [line items] |
Property plant and equipment depreciation rate | 3.33%
Generator [member] | Generation unit [member] |
Disclosure of detailed information about property, plant and equipment [line items] |
Property plant and equipment depreciation rate | 3.33%
Water turbine [member] | Generation unit [member] |
Disclosure of detailed information about property, plant and equipment [line items] |
Property plant and equipment depreciation rate | 2.50%
Pressure tunnel [member] | Generation unit [member] |
Disclosure of detailed information about property, plant and equipment [line items] |
Property plant and equipment depreciation rate | 3.13%
Command station, panel and cubicle [member] | Generation unit [member] |
Disclosure of detailed information about property, plant and equipment [line items] |
Property plant and equipment depreciation rate | 3.57%
Floodgate [member] | Generation unit [member] |
Disclosure of detailed information about property, plant and equipment [line items] |
Property plant and equipment depreciation rate | 3.33%
Software [member] | Administration unit [member] |
Disclosure of detailed information about property, plant and equipment [line items] |
Property plant and equipment depreciation rate | 20.00%
Vehicles [member] | Administration unit [member] |
Disclosure of detailed information about property, plant and equipment [line items] |
Property plant and equipment depreciation rate | 14.29%
IT equipment in general [member] | Administration unit [member] |
Disclosure of detailed information about property, plant and equipment [line items] |
Property plant and equipment depreciation rate | 16.67%
General Equipment [member] | Administration unit [member] |
Disclosure of detailed information about property, plant and equipment [line items] |
Property plant and equipment depreciation rate | 6.25%

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- Definition Property plant and equipment depreciation rate. + References No definition available. + Details
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Balance Type: | na
Period Type: | duration

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

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

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- Details
Name: | ifrs-full_ClassesOfPropertyPlantAndEquipmentAxis=cig_BuildingsMachineRoomMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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- Details
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- Details
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Namespace Prefix: |
Data Type: | na
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- Details
Name: | ifrs-full_ClassesOfPropertyPlantAndEquipmentAxis=cig_WaterTurbineMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | ifrs-full_ClassesOfPropertyPlantAndEquipmentAxis=cig_PressureTunnelMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | ifrs-full_ClassesOfPropertyPlantAndEquipmentAxis=cig_CommandStationPanelAndCubicleMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | ifrs-full_ClassesOfPropertyPlantAndEquipmentAxis=cig_FloodgateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | ifrs-full_ClassesOfPropertyPlantAndEquipmentAxis=ifrs-full_ComputerSoftwareMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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- Details
Name: | ifrs-full_ClassesOfPropertyPlantAndEquipmentAxis=cig_ITEquipmentInGeneralMember
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- Details
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