XML 129 R106.htm IDEA: XBRL DOCUMENT
v3.20.4

Financial instruments - Natural gas forward contracts (Details) MMBTU in Thousands | 12 Months Ended | 36 Months Ended | 48 Months Ended | 108 Months Ended |
--- | --- | --- | --- | --- | ---
Dec. 31, 2020 USD ($) $ / MMBTU | Dec. 31, 2029 MMBTU | Jan. 01, 2025 MMBTU | Jan. 01, 2032 MMBTU | Dec. 31, 2019 USD ($) $ / MMBTU
Disclosure of financial assets [line items] |  |  |  |  |
Reclassification of hedge | $ 20,271,000 |  |  |  |
Accumulated other comprehensive income |  |  |  |  |
Disclosure of financial assets [line items] |  |  |  |  |
Reclassification of hedge | 20,271,000 |  |  |  |
Natural gas forward contract |  |  |  |  |
Disclosure of financial assets [line items] |  |  |  |  |
Hedging instrument, energy (in mmbtu) | MMBTU |  | 30 | 40 | 50 |
Hedge ineffectiveness | 0 |  |  |  |
Natural gas forward contract | Cash flow hedges |  |  |  |  |
Disclosure of financial assets [line items] |  |  |  |  |
Notional amount | 1,005,600,000 |  |  |  | $ 969,600,000
Negative fair value | $ 177,400,000 |  |  |  | $ 195,100,000
Natural gas forward contract | Cash flow hedges | Geismar Facility |  |  |  |  |
Disclosure of financial assets [line items] |  |  |  |  |
Average contract price (in usd per mmbtu) | $ / MMBTU | 3.36 |  |  |  | 3.45
Natural gas forward contract | Cash flow hedges | Medicine Hat Facility |  |  |  |  |
Disclosure of financial assets [line items] |  |  |  |  |
Average contract price (in usd per mmbtu) | $ / MMBTU | 1.96 |  |  |  | 1.96
Natural gas forward contract | Cash flow hedges | other current liabilities |  |  |  |  |
Disclosure of financial assets [line items] |  |  |  |  |
Negative fair value | $ 14,800,000 |  |  |  |
Natural gas forward contract | Cash flow hedges | Other non-current liabilities |  |  |  |  |
Disclosure of financial assets [line items] |  |  |  |  |
Negative fair value | 166,000,000.0 |  |  |  |
Natural gas forward contract | Cash flow hedges | other current assets |  |  |  |  |
Disclosure of financial assets [line items] |  |  |  |  |
Positive fair value | 400,000 |  |  |  |
Natural gas forward contract | Cash flow hedges | Other non-current asset |  |  |  |  |
Disclosure of financial assets [line items] |  |  |  |  |
Positive fair value | 3,000,000.0 |  |  |  |
Natural gas forward contract | Accumulated other comprehensive income |  |  |  |  |
Disclosure of financial assets [line items] |  |  |  |  |
Reclassification of hedge | $ 20,300,000 |  |  |  |

X
- Definition The average price of a hedging instrument. [Refer: Hedging instruments [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2020-01-01 -Paragraph 23B -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2020-en-r&anchor=para_23B_b&doctype=Standard -URIDate 2020-01-01 + Details
Name: | ifrs-full_AveragePriceOfHedgingInstrument
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- 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_DisclosureOfFinancialAssetsLineItems
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The fair value of financial assets. [Refer: At fair value [member]; Financial assets] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2020-01-01 -Paragraph 25 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2020-en-r&anchor=para_25&doctype=Standard -URIDate 2020-01-01 + Details
Name: | ifrs-full_FinancialAssetsAtFairValue
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The fair value of financial liabilities. [Refer: At fair value [member]; Financial liabilities] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2020-01-01 -Paragraph 25 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2020-en-r&anchor=para_25&doctype=Standard -URIDate 2020-01-01 + Details
Name: | ifrs-full_FinancialLiabilitiesAtFairValue
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The gain (loss) on hedge ineffectiveness. Hedge ineffectiveness is the extent to which the changes in the fair value or the cash flows of the hedging instrument are greater or less than those on the hedged item. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2020-01-01 -Paragraph 24C -Subparagraph a -Clause i -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2020-en-r&anchor=para_24C_a_i&doctype=Standard -URIDate 2020-01-01 + Details
Name: | ifrs-full_GainLossOnHedgeIneffectiveness
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The nominal or face amount of a financial instrument, used to calculate payments made on that instrument. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 112 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_112_c&doctype=Standard -URIDate 2020-01-01 + Details
Name: | ifrs-full_NotionalAmount
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

X
- Definition Hedging instrument, energy + References No definition available. + Details
Name: | mx_HedgingInstrumentEnergy
Namespace Prefix: | mx_
Data Type: | num:energyItemType
Balance Type: | na
Period Type: | duration

X
- Definition Increase (decrease) through realized hedge losses recognized in cash flow hedges, equity + References No definition available. + Details
Name: | mx_IncreaseDecreaseThroughRealizedHedgeLossesRecognizedInCashFlowHedgesEquity
Namespace Prefix: | mx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | ifrs-full_ComponentsOfEquityAxis=ifrs-full_AccumulatedOtherComprehensiveIncomeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ClassesOfFinancialLiabilitiesAxis=mx_NaturalGasForwardContractMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TypesOfHedgesAxis=ifrs-full_CashFlowHedgesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | mx_RealEstateAndAccumulatedDepreciationDescriptionOfProperty1Axis=mx_GeismarFacilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | mx_RealEstateAndAccumulatedDepreciationDescriptionOfProperty1Axis=mx_MedicineHatFacilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | mx_BalanceSheetLocationAxis=mx_OtherCurrentLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | mx_BalanceSheetLocationAxis=mx_OtherNonCurrentLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | mx_BalanceSheetLocationAxis=mx_OtherCurrentAssetsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | mx_BalanceSheetLocationAxis=mx_OtherNonCurrentAssetMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |