Financial risk management - Foreign currency risk (Details) - Currency risk - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021
Disclosure of financial instruments by type of interest rate [line items]
Net working capital asset	$ 69.9	$ 148.4
Reasonably possible change in risk variable, percent	10.00%
Impact on value of net working capital	$ 7.0	$ 14.8

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table.

No definition available.

+ Details

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

- Definition

The amount of risk exposure associated with financial instruments with a shared characteristic that identifies a concentration of risks. [Refer: Financial instruments, class [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2022-03-24
-Paragraph B8
-Subparagraph c
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2022-en-r&anchor=para_B8_c&doctype=Appendix&subtype=B
-URIDate 2022-03-24

+ Details

Name:	ifrs-full_RiskExposureAssociatedWithInstrumentsSharingCharacteristic
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Change In Risk Variable, Impact On Equity

+ References

No definition available.

+ Details

Name:	mx_SensitivityAnalysisForTypesOfMarketRiskReasonablyPossibleChangeInRiskVariableImpactOnEquity
Namespace Prefix:	mx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Change In Risk Variable, Percent

+ References

No definition available.

+ Details

Name:	mx_SensitivityAnalysisForTypesOfMarketRiskReasonablyPossibleChangeInRiskVariablePercent
Namespace Prefix:	mx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	ifrs-full_TypesOfRisksAxis=ifrs-full_CurrencyRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: