The adjustment to the basis (reference rate) used for calculation of the interest rate on borrowings. [Refer: Borrowings]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 7
-IssueDate 2023-01-01
-Paragraph 7
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2023-en-r&anchor=para_7&doctype=Standard
-URIDate 2023-03-23

+ Details

Name:	ifrs-full_BorrowingsAdjustmentToInterestRateBasis
Namespace Prefix:	ifrs-full_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of undrawn borrowing facilities that may be available for future operating activities and to settle capital commitments. [Refer: Capital commitments]

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 7
-IssueDate 2023-01-01
-Paragraph 50
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=7&code=ifrs-tx-2023-en-r&anchor=para_50_a&doctype=Standard
-URIDate 2023-03-23

+ Details

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

- Definition

Amount of equity method investment income.

+ References

No definition available.

+ Details

Name:	mag_EquityMethodInvestmentIncome
Namespace Prefix:	mag_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

No definition available.

+ Details

Name:	mag_EquityMethodInvestmentOwnershipPercentage1
Namespace Prefix:	mag_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the impact on earnings excluding currency exposure related taxes.

+ References

No definition available.

+ Details

Name:	mag_ImpactOnEarningsExcludingCurrencyExposureRelatedTaxes
Namespace Prefix:	mag_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of assets less the amount of liabilities, denominated in foreign currencies.

+ References

No definition available.

+ Details

Name:	mag_NetAssetsLiabilitiesDenominatedInForeignCurrencies
Namespace Prefix:	mag_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The percentage change in foreign exchange rates.

+ References

No definition available.

+ Details

Name:	mag_PercentageChangeInForeignExchangeRates
Namespace Prefix:	mag_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

Name:	mag_Statement1LineItems
Namespace Prefix:	mag_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	ifrs-full_TypesOfInterestRatesAxis=mag_SecuredOvernightFinancingRateSOFRMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	ifrs-full_GeographicalAreasAxis=country_MX
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_BorrowingsByNameAxis=mag_SeniorSecuredRevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_SignificantInvestmentsInAssociatesAxis=mag_JuanicipioMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 15 - Financial Risk Management (Details Textual) $ in Thousands, $ in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2023 CAD ($)	Dec. 31, 2023 MXN ($)	Oct. 04, 2023 USD ($)	Dec. 31, 2022 CAD ($)	Dec. 31, 2022 MXN ($)
Secured overnight financing rate (SOFR) [member] \| Bottom of range [member]
Statement Line Items [Line Items]
Borrowings, adjustment to interest rate basis	2.00%		2.00%	2.00%
Secured overnight financing rate (SOFR) [member] \| Top of range [member]
Statement Line Items [Line Items]
Borrowings, adjustment to interest rate basis	4.00%		4.00%	4.00%
MEXICO
Statement Line Items [Line Items]
Net assets liabilities denominated in foreign currencies				$ 564			$ 8,900
Percentage change in foreign exchange rates	10.00%		10.00%	10.00%
Country of domicile [member]
Statement Line Items [Line Items]
Net assets liabilities denominated in foreign currencies			$ 1.4			$ 1.1
Percentage change in foreign exchange rates	10.00%		10.00%	10.00%
Impact on earnings excluding currency exposure related taxes	$ 160
Senior secured revolving credit facility [member]
Statement Line Items [Line Items]
Undrawn borrowing facilities					$ 40,000
Senior secured revolving credit facility [member] \| Top of range [member]
Statement Line Items [Line Items]
Undrawn borrowing facilities					$ 75,000
Senior secured revolving credit facility [member] \| Secured overnight financing rate (SOFR) [member] \| Bottom of range [member]
Statement Line Items [Line Items]
Borrowings, adjustment to interest rate basis					2.00%
Senior secured revolving credit facility [member] \| Secured overnight financing rate (SOFR) [member] \| Top of range [member]
Statement Line Items [Line Items]
Borrowings, adjustment to interest rate basis					4.00%
Juanicipio [member]
Statement Line Items [Line Items]
Equity method investment, ownership percentage	44.00%	44.00%	44.00%	44.00%		44.00%	44.00%
Net assets liabilities denominated in foreign currencies				$ 545,000			$ 744,000
Percentage change in foreign exchange rates	10.00%		10.00%	10.00%
Impact on earnings excluding currency exposure related taxes	$ (3,584)	$ (4,269)
Equity method investment income	$ (1,577)	$ (1,878)