XML 151 R91.htm IDEA: XBRL DOCUMENT
v3.20.1

Share-based compensation - Range of exercise prices in SARs and TSARs (Details) | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2019 shares $ / shares | Dec. 31, 2018 shares $ / shares | Dec. 31, 2017 shares $ / shares
SARs |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average remaining contractual life (years) | 2 years 11 months 19 days |  |
Number of units outstanding (in shares) | shares | 857,407 | 896,883 | 1,450,077
Weighted average exercise price of units outstanding (in usd per unit) | $ 52.02 | $ 51.27 | $ 45.11
Number of units exercisable (in shares) | shares | 691,336 |  |
Weighted average exercise price of units exercisable (in usd per unit) | $ 51.50 |  |
SARs | $25.97 to $35.51 |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average remaining contractual life (years) | 3 years 2 months 1 day |  |
Number of units outstanding (in shares) | shares | 186,980 |  |
Weighted average exercise price of units outstanding (in usd per unit) | $ 34.59 |  |
Number of units exercisable (in shares) | shares | 186,980 |  |
Weighted average exercise price of units exercisable (in usd per unit) | $ 34.59 |  |
SARs | $25.97 to $35.51 | Minimum |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average exercise price of units outstanding (in usd per unit) | 25.97 |  |
SARs | $25.97 to $35.51 | Maximum |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average exercise price of units outstanding (in usd per unit) | $ 35.51 |  |
SARs | $38.24 to $50.17 |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average remaining contractual life (years) | 2 years 10 months 28 days |  |
Number of units outstanding (in shares) | shares | 191,684 |  |
Weighted average exercise price of units outstanding (in usd per unit) | $ 46.39 |  |
Number of units exercisable (in shares) | shares | 141,597 |  |
Weighted average exercise price of units exercisable (in usd per unit) | $ 45.07 |  |
SARs | $38.24 to $50.17 | Minimum |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average exercise price of units outstanding (in usd per unit) | 38.24 |  |
SARs | $38.24 to $50.17 | Maximum |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average exercise price of units outstanding (in usd per unit) | $ 50.17 |  |
SARs | $54.65 to $78.59 |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average remaining contractual life (years) | 2 years 10 months 28 days |  |
Number of units outstanding (in shares) | shares | 478,743 |  |
Weighted average exercise price of units outstanding (in usd per unit) | $ 61.08 |  |
Number of units exercisable (in shares) | shares | 362,759 |  |
Weighted average exercise price of units exercisable (in usd per unit) | $ 62.73 |  |
SARs | $54.65 to $78.59 | Minimum |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average exercise price of units outstanding (in usd per unit) | 54.65 |  |
SARs | $54.65 to $78.59 | Maximum |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average exercise price of units outstanding (in usd per unit) | $ 78.59 |  |
TSARs |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average remaining contractual life (years) | 3 years 9 months 7 days |  |
Number of units outstanding (in shares) | shares | 1,661,327 | 1,447,301 | 2,043,495
Weighted average exercise price of units outstanding (in usd per unit) | $ 52.55 | $ 51.24 | $ 46.62
Number of units exercisable (in shares) | shares | 1,054,262 |  |
Weighted average exercise price of units exercisable (in usd per unit) | $ 51.05 |  |
TSARs | $25.97 to $35.51 |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average remaining contractual life (years) | 3 years 2 months 1 day |  |
Number of units outstanding (in shares) | shares | 308,837 |  |
Weighted average exercise price of units outstanding (in usd per unit) | $ 34.59 |  |
Number of units exercisable (in shares) | shares | 308,837 |  |
Weighted average exercise price of units exercisable (in usd per unit) | $ 34.59 |  |
TSARs | $25.97 to $35.51 | Minimum |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average exercise price of units outstanding (in usd per unit) | 25.97 |  |
TSARs | $25.97 to $35.51 | Maximum |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average exercise price of units outstanding (in usd per unit) | $ 35.51 |  |
TSARs | $38.24 to $50.17 |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average remaining contractual life (years) | 3 years 6 months 7 days |  |
Number of units outstanding (in shares) | shares | 386,471 |  |
Weighted average exercise price of units outstanding (in usd per unit) | $ 47.62 |  |
Number of units exercisable (in shares) | shares | 263,269 |  |
Weighted average exercise price of units exercisable (in usd per unit) | $ 46.82 |  |
TSARs | $38.24 to $50.17 | Minimum |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average exercise price of units outstanding (in usd per unit) | 38.24 |  |
TSARs | $38.24 to $50.17 | Maximum |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average exercise price of units outstanding (in usd per unit) | $ 50.17 |  |
TSARs | $54.65 to $78.59 |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average remaining contractual life (years) | 4 years 22 days |  |
Number of units outstanding (in shares) | shares | 966,019 |  |
Weighted average exercise price of units outstanding (in usd per unit) | $ 60.27 |  |
Number of units exercisable (in shares) | shares | 482,156 |  |
Weighted average exercise price of units exercisable (in usd per unit) | $ 63.91 |  |
TSARs | $54.65 to $78.59 | Minimum |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average exercise price of units outstanding (in usd per unit) | 54.65 |  |
TSARs | $54.65 to $78.59 | Maximum |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |
Weighted average exercise price of units outstanding (in usd per unit) | $ 78.59 |  |

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

X
- Definition The number of other equity instruments (ie other than share options) exercisable in a share-based payment arrangement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IFRS -Number 2 -IssueDate 2019-01-01 -Paragraph 45 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2019-en-r&anchor=para_45&doctype=Standard -URIDate 2019-03-27 + Details
Name: | ifrs-full_NumberOfOtherEquityInstrumentsExercisableInSharebasedPaymentArrangement
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition The number of other equity instruments (ie other than share options) outstanding in a share-based payment arrangement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IFRS -Number 2 -IssueDate 2019-01-01 -Paragraph 45 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2019-en-r&anchor=para_45&doctype=Standard -URIDate 2019-03-27 + Details
Name: | ifrs-full_NumberOfOtherEquityInstrumentsOutstandingInSharebasedPaymentArrangement
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition The weighted average exercise price of other equity instruments (ie other than share options) exercisable in a share-based payment arrangement. [Refer: Weighted average [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IFRS -Number 2 -IssueDate 2019-01-01 -Paragraph 45 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2019-en-r&anchor=para_45&doctype=Standard -URIDate 2019-03-27 + Details
Name: | ifrs-full_WeightedAverageExercisePriceOfOtherEquityInstrumentsExercisableInSharebasedPaymentArrangement2019
Namespace Prefix: | ifrs-full_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition The weighted average exercise price of other equity instruments (ie other than share options) outstanding in a share-based payment arrangement. [Refer: Weighted average [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IFRS -Number 2 -IssueDate 2019-01-01 -Paragraph 45 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2019-en-r&anchor=para_45&doctype=Standard -URIDate 2019-03-27 + Details
Name: | ifrs-full_WeightedAverageExercisePriceOfOtherEquityInstrumentsOutstandingInSharebasedPaymentArrangement2019
Namespace Prefix: | ifrs-full_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition Weighted Average Remaining Contractual Life Of Outstanding Other Equity Instruments + References No definition available. + Details
Name: | mx_WeightedAverageRemainingContractualLifeOfOutstandingOtherEquityInstruments
Namespace Prefix: | mx_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=mx_ShareAppreciationRightsSARMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | mx_RangesOfExercisePricesForOutstandingOtherEquityInstrumentsAxis=mx_ExercisePriceRangeOneMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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

X
- Details
Name: | mx_RangesOfExercisePricesForOutstandingOtherEquityInstrumentsAxis=mx_ExercisePriceRangeTwoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | mx_RangesOfExercisePricesForOutstandingOtherEquityInstrumentsAxis=mx_ExercisePriceRangeThreeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=mx_TandemShareAppreciationRightsTSARMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |