The applicable income tax rate.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2019-01-01
-Paragraph 81
-Subparagraph c
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2019-en-r&anchor=para_81_c_ii&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_ApplicableTaxRate
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The description of the expiry date (if any) of deductible temporary differences, unused tax losses and unused tax credits for which no deferred tax asset is recognised in the statement of financial position. [Refer: Temporary differences [member]; Unused tax credits [member]; Unused tax losses [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2019-01-01
-Paragraph 81
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2019-en-r&anchor=para_81_e&doctype=Standard
-URIDate 2019-03-27

+ Details

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

- 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

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

- Definition

The amount that represents the difference between the tax expense (income) and the product of the accounting profit multiplied by the applicable tax rate(s) that relates to tax losses. [Refer: Accounting profit]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2019-01-01
-Paragraph 81
-Subparagraph c
-Clause i
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2019-en-r&anchor=para_81_c_i&doctype=Standard
-URIDate 2019-03-27

+ Details

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

- Definition

Amount of tax payments and expenses increase (decrease) during the year.

+ References

No definition available.

+ Details

Name:	simecb_AmountOfTaxPaymentsAndExpensesIncreaseDecrease
Namespace Prefix:	simecb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Description of decree issued by finance ministry.

+ References

No definition available.

+ Details

Name:	simecb_DescriptionOfDecreeIssuedByFinanceMinistry
Namespace Prefix:	simecb_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of investment of new fixed assets.

+ References

No definition available.

+ Details

Name:	simecb_PercentageOfInvestmentOfNewFixedAssets
Namespace Prefix:	simecb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	ifrs-full_TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis=simecb_GVDOBrasilIndustriaComercioOfAcoLTDAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis=simecb_CompanhiaSiderurgicaDoEspiritoSantoSAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CurrencyAxis=currency_USD
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CurrencyAxis=currency_BRL
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_GeographicalAreasAxis=ifrs-full_CountryOfDomicileMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_NonadjustingEventsAfterReportingPeriodAxis=simecb_IncomeTaxEstimatedRecoveryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_GeographicalAreasAxis=simecb_RepublicMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_GeographicalAreasAxis=simecb_StateAndLocalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_GeographicalAreasAxis=country_CA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Income taxes (Narrative) (Details) R$ in Thousands, $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 MXN ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 MXN ($)	Dec. 31, 2019 BRL (R$)	Dec. 31, 2018 MXN ($)	Dec. 31, 2018 BRL (R$)	Dec. 31, 2017	Dec. 31, 2016
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Effective tax rate		54.26%	54.26%	54.26%	17.92%	17.92%	37.21%
Amount of tax payments and expenses increase (decrease)			$ 2,323,700
GV do Brasil Industria e Comercio of Aco LTDA [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Tax losses			985,000		$ 1,025,000
Companhia Siderurgica do Espirito Santo S.A. [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Tax losses			94,000
USD [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Tax losses			$ 9,268,569
Brazil, Brazil Real [Member] \| GV do Brasil Industria e Comercio of Aco LTDA [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Tax losses \| R$				R$ 210,345		R$ 202,008
Brazil, Brazil Real [Member] \| Companhia Siderurgica do Espirito Santo S.A. [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Tax losses \| R$				R$ 20,042
Mexican companies [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Effective tax rate		30.00%	30.00%	30.00%	30.00%	30.00%
Description of decree issued by finance ministry		As of November 18, 2015, the Finance Ministry (SHCP) issued a decree in which a fiscal incentive is given to those who pay income tax (ISR) under terms of the Titles II or IV, Chapter II, Section I of the Law of ISR. Taxpayers who had business income of up to 100 million pesos,	As of November 18, 2015, the Finance Ministry (SHCP) issued a decree in which a fiscal incentive is given to those who pay income tax (ISR) under terms of the Titles II or IV, Chapter II, Section I of the Law of ISR. Taxpayers who had business income of up to 100 million pesos,	As of November 18, 2015, the Finance Ministry (SHCP) issued a decree in which a fiscal incentive is given to those who pay income tax (ISR) under terms of the Titles II or IV, Chapter II, Section I of the Law of ISR. Taxpayers who had business income of up to 100 million pesos,
Percentage of investment of new fixed assets		69.00%	69.00%	69.00%			85.00%	82.00%
Amount of tax payments and expenses increase (decrease)			$ 2,323,700
Mexican companies [Member] \| Income Tax Estimated Recovery [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Amount of tax payments and expenses increase (decrease)	$ 554,400
Republic [Member] \| USD [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Tax losses		$ 249,700
Expiration period		expire between 2033 and 2038	expire between 2033 and 2038	expire between 2033 and 2038
State and local [Member] \| USD [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Tax losses		$ 323,600
Expiration period		expire between 2020 and 2039	expire between 2020 and 2039	expire between 2020 and 2039
Canada [Member] \| USD [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Tax losses		$ 5,500
Expiration period		expire between 2032 and 2039	expire between 2032 and 2039	expire between 2032 and 2039