Name:	fsm_FairValueOfNumberOfOtherEquityInstrumentsGrantedInShareBasedPaymentArrangement
Namespace Prefix:	fsm_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

Fair value per share granted options.

No definition available.

Name:	fsm_FairValuePerShareGrantedOptions
Namespace Prefix:	fsm_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

Number of shares authorized for issuance under share-based payment arrangement.

No definition available.

Name:	fsm_IfrsShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
Namespace Prefix:	fsm_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

No definition available.

Name:	fsm_IfrsShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Namespace Prefix:	fsm_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Vesting tranche percentage sharebased arrangements.

No definition available.

Name:	fsm_VestingTranchePercentageSharebasedArrangements
Namespace Prefix:	fsm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

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.

No definition available.

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The amount of expense from share-based payment transactions with employees.

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

Name:	ifrs-full_ExpenseFromSharebasedPaymentTransactionsWithEmployees
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The number of other equity instruments (ie other than share options) granted in a share-based payment arrangement.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2020-01-01
-Paragraph 47
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2020-en-r&anchor=para_47_b&doctype=Standard
-URIDate 2020-01-01

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 2
-IssueDate 2020-01-01
-Paragraph 45
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2020-en-r&anchor=para_45&doctype=Standard
-URIDate 2020-01-01

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

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Namespace Prefix:
Data Type:	na
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Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=fsm_EquitySettledRestrictedShareUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=fsm_PerformanceShareUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=fsm_IfrsShareBasedPaymentArrangementOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	fsm_VestingTrancheAxis=fsm_VestingTrancheOnePeriodMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=fsm_RestrictedShareUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	fsm_VestingTrancheAxis=fsm_VestingTrancheTwoPeriodMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	fsm_VestingTrancheAxis=fsm_VestingTrancheThreePeriodMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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