The term of environmental impact authorization.

No definition available.

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

No definition available.

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Increase (decrease) in debt instrument borrowing capacity

+ References

No definition available.

+ Details

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Namespace Prefix:	fsm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The percentage of hedging instrument.

+ References

No definition available.

+ Details

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- Definition

The threshold amount of investments and financial assistance to non guaranteeing subsidiaries.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

- Definition

Threshold balance of cash to be maintained for increase in borrowing capacity.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

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.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
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Period Type:	duration

- Definition

The amount of loans received.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2022-03-24
-Paragraph 112
-Subparagraph c
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2022-en-r&anchor=para_112_c&doctype=Standard
-URIDate 2022-03-24

+ Details

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

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=fsm_ScenarioDebtInstrumentCovenantFailToMaintainMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	fsm_TypeOfCommodityAxis=fsm_GoldCommodityTypeMember
Namespace Prefix:
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SUBSEQUENT EVENTS (Details) - USD ($)		5 Months Ended
SUBSEQUENT EVENTS (Details) - USD ($)	Jan. 05, 2023	Jun. 30, 2023	Dec. 31, 2022	Dec. 15, 2022	Dec. 14, 2022	Dec. 31, 2021	Nov. 05, 2021	Nov. 04, 2021	Dec. 31, 2020
Disclosure of non-adjusting events after reporting period [line items]
Debt outstanding			$ 219,175,000			$ 157,489,000			$ 158,616,000
Amended Credit Facility [Member]
Disclosure of non-adjusting events after reporting period [line items]
Borrowing capacity				$ 250,000,000.0	$ 200,000,000.0		$ 200,000,000.0	$ 120,000,000.0
Annulment of Environmental Impact Authorization [Member]
Disclosure of non-adjusting events after reporting period [line items]
Extension term	12 years
Annulment of Environmental Impact Authorization [Member] \| Amended Credit Facility [Member] \| Top of range [member]
Disclosure of non-adjusting events after reporting period [line items]
Threshold amount of investments and financial assistance to non guaranteeing subsidiaries	$ 3,000,000
Annulment of Environmental Impact Authorization [Member] \| Scenario, Receipt of Definitive Injunction [Member] \| Amended Credit Facility [Member]
Disclosure of non-adjusting events after reporting period [line items]
Increase (decrease) in debt instrument borrowing capacity	50,000,000
Annulment of Environmental Impact Authorization [Member] \| Scenario, Debt Instrument Covenant [Member] \| Amended Credit Facility [Member]
Disclosure of non-adjusting events after reporting period [line items]
Borrowing capacity	250,000,000
Cash	70,000,000
Annulment of Environmental Impact Authorization [Member] \| Scenario, Debt Instrument Covenant Fail To Maintain [Member] \| Amended Credit Facility [Member]
Disclosure of non-adjusting events after reporting period [line items]
Borrowing capacity	$ 200,000,000
Annulment of Environmental Impact Authorization [Member] \| Gold Commodity Type [member]
Disclosure of non-adjusting events after reporting period [line items]
Percentage of hedging Instrument		25.00%