Note 8 - Property and Equipment and Leases - Minimum Lease Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Statement Line Items [Line Items]
Less than one year	$ 153
Two to three years	306
Four to five years	160
Thereafter
Undiscounted minimum lease payments	619
Effect of discounting	(143)
Present value of minimum lease payments - total lease obligation	476
Less: current portion	(93)	$ (74)
Long-term lease obligation	$ 383	$ 467

The amount of current lease liabilities. [Refer: Lease liabilities]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 16
-IssueDate 2020-01-01
-Paragraph 47
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=16&code=ifrs-tx-2020-en-r&anchor=para_47_b&doctype=Standard
-URIDate 2020-01-01

+ Details

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

- Definition

The amount of liabilities related to the entity's leases. Lease is a contract, or part of a contract, that conveys the right to use an underlying asset for a period of time in exchange for consideration.

+ References

+ Details

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

- Definition

The amount of non-current lease liabilities. [Refer: Lease liabilities]

+ References

+ Details

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

- Definition

The effect of discounting on lease liability.

+ References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Represents undiscounted minimum lease payments.

+ References

No definition available.

+ Details

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Namespace Prefix:	mag_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents undiscounted minimum lease payments later than five years.

+ References

No definition available.

+ Details

Name:	mag_UndiscountedMinimumLeasePaymentsLaterThanFiveYears
Namespace Prefix:	mag_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents undiscounted minimum lease payments later than one year and not later than three years.

+ References

No definition available.

+ Details

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Namespace Prefix:	mag_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents undiscounted minimum lease payments later than three years and not later than five years.

+ References

No definition available.

+ Details

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Namespace Prefix:	mag_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Represents undiscounted minimum lease payments not later than one year.

+ References

No definition available.

+ Details

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Namespace Prefix:	mag_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant