Non-Controlling Interest in Consolidate Subsidiaries - AOCI (Details) $ in Millions, $ in Millions	Dec. 31, 2020 USD ($)	Dec. 31, 2020 MXN ($)	Dec. 31, 2019 MXN ($)
Disclosure Of Non Controlling Interest In Consolidated Subsidiaries [line items]
Accumulated other comprehensive income, total	$ (43)	$ (843)	$ 685
Non-controlling interest [member]
Disclosure Of Non Controlling Interest In Consolidated Subsidiaries [line items]
Reserve of exchange differences on translation		(6,657)	(699)
Reserve of remeasurements of defined benefit plans		(559)	(390)
Reserve of cash flow hedges		(277)	(611)
Accumulated other comprehensive income, total		$ (7,493)	$ (1,700)

Disclosure of non controlling interest in consolidated subsidiaries line items.

No definition available.

Name:	fmx_DisclosureOfNonControllingInterestInConsolidatedSubsidiariesLineItems
Namespace Prefix:	fmx_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of accumulated items of income and expense (including reclassification adjustments) that are not recognised in profit or loss as required or permitted by other IFRSs. [Refer: IFRSs [member]; Other comprehensive income]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2020-01-01
-Paragraph 55
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_55&doctype=Standard
-URIDate 2020-01-01

+ Details

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

- Definition

A component of equity representing the accumulated portion of gain (loss) on a hedging instrument that is determined to be an effective hedge for cash flow hedges. [Refer: Cash flow hedges [member]]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2020-01-01
-Paragraph 78
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_78_e&doctype=Standard
-URIDate 2020-01-01

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 9
-IssueDate 2020-01-01
-Paragraph 6.5.11
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=9&code=ifrs-tx-2020-en-r&anchor=para_6.5.11&doctype=Standard
-URIDate 2020-01-01

+ Details

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

- Definition

A component of equity representing exchange differences on translation of financial statements of foreign operations recognised in other comprehensive income and accumulated in equity. [Refer: Other comprehensive income]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 21
-IssueDate 2020-01-01
-Paragraph 52
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=21&code=ifrs-tx-2020-en-r&anchor=para_52_b&doctype=Standard
-URIDate 2020-01-01

+ Details

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

- Definition

A component of equity representing the accumulated remeasurements of defined benefit plans. [Refer: Defined benefit plans [member]]

+ References

+ Details

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

- Details

Name:	ifrs-full_ComponentsOfEquityAxis=ifrs-full_NoncontrollingInterestsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: