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v3.21.1

Employee Benefits - Trust Assets (Detail) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019
Mexican subsidiaries [member] |  |
Variable return: |  |
Plan asset investment for related parties, percentage | 10.00% |
Federal government instruments of the respective countries [member] | Bottom of range [member] |  |
Variable return: |  |
Fund assets, percentage | 30.00% |
Level 1 [member] |  |
Variable return: |  |
Trust assets fixed and variable return percentage | 100.00% | 100.00%
Level 1 [member] | Traded Securities [member] |  |
Fixed return: |  |
Trust assets fixed return percentage | 27.00% | 9.00%
Level 1 [member] | Bank instruments [member] |  |
Fixed return: |  |
Trust assets fixed return percentage | 9.00% | 23.00%
Level 1 [member] | Federal government instruments of the respective countries [member] |  |
Fixed return: |  |
Trust assets fixed return percentage | 29.00% | 33.00%
Level 1 [member] | Publicly traded shares [member] |  |
Variable return: |  |
Trust assets variable return percentage | 35.00% | 35.00%

X
- Definition Fixed return. + References No definition available. + Details
Name: | fmx_FixedReturnAbstract
Namespace Prefix: | fmx_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Percentage of fund assets. + References No definition available. + Details
Name: | fmx_PercentageOfFundAssets
Namespace Prefix: | fmx_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Percentage of plan asset investment for related parties. + References No definition available. + Details
Name: | fmx_PercentageOfPlanAssetInvestmentForRelatedParties
Namespace Prefix: | fmx_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Trust assets fixed and variable return percentage. + References No definition available. + Details
Name: | fmx_TrustAssetsFixedAndVariableReturnPercentage
Namespace Prefix: | fmx_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition Trust assets fixed return percentage. + References No definition available. + Details
Name: | fmx_TrustAssetsFixedReturnPercentage
Namespace Prefix: | fmx_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition Trust assets variable return percentage. + References No definition available. + Details
Name: | fmx_TrustAssetsVariableReturnPercentage
Namespace Prefix: | fmx_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Variable return. + References No definition available. + Details
Name: | fmx_VariableReturnAbstract
Namespace Prefix: | fmx_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | ifrs-full_CategoriesOfRelatedPartiesAxis=ifrs-full_SubsidiariesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | ifrs-full_ClassesOfFinancialAssetsAxis=fmx_FederalGovernmentInstrumentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | ifrs-full_RangeAxis=ifrs-full_BottomOfRangeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | ifrs-full_LevelsOfFairValueHierarchyAxis=ifrs-full_Level1OfFairValueHierarchyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | ifrs-full_ClassesOfFinancialAssetsAxis=fmx_TradedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | ifrs-full_ClassesOfFinancialAssetsAxis=fmx_BankInstrumentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | ifrs-full_ClassesOfFinancialAssetsAxis=fmx_PubliclyTradedSharesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |