Name:	fmst_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight1
Namespace Prefix:	fmst_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Represents the value of deferred gain on spin out transaction as of balance sheet date.

No definition available.

Name:	fmst_DeferredGainOnSpinOutTransaction
Namespace Prefix:	fmst_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount of gain/loss on a spin-out transaction.

No definition available.

Name:	fmst_GainLossOnSpinoutTransaction
Namespace Prefix:	fmst_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The market target price of share options granted.

No definition available.

Name:	fmst_MarketTargetPriceShareOptionsGranted
Namespace Prefix:	fmst_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

The number of options received as the result of an exchange.

No definition available.

Name:	fmst_NumberOfOptionsReceivedInExchange
Namespace Prefix:	fmst_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

The number of options to be transferred and exchanged.

No definition available.

Name:	fmst_NumberOfOptionsToBeTransferredAndExchanged
Namespace Prefix:	fmst_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

The number of units to be transferred and exchanged.

No definition available.

Name:	fmst_NumberOfUnitsToBeTransferredAndExchanged
Namespace Prefix:	fmst_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

The number of warrants issued during the period.

No definition available.

Name:	fmst_NumberOfWarrantsIssuedDuringThePeriod
Namespace Prefix:	fmst_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

Name:	fmst_Statement1LineItems
Namespace Prefix:	fmst_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Represents the fair value of warrants issued during the period.

No definition available.

Name:	fmst_WarrantsIssuedFairValue
Namespace Prefix:	fmst_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The amount of outstanding funds that the entity is obligated to repay.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2024-01-01
-Paragraph 55
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2024-en-r&anchor=para_55&doctype=Standard
-URIDate 2024-03-27

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The interest rate on borrowings. [Refer: Borrowings]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 7
-IssueDate 2024-01-01
-Paragraph 7
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2024-en-r&anchor=para_7&doctype=Standard
-URIDate 2024-03-27

Name:	ifrs-full_BorrowingsInterestRate
Namespace Prefix:	ifrs-full_
Data Type:	dtr-2022:percentItemType
Balance Type:	na
Period Type:	instant

The amount of expense arising from share-based payment transactions in which the goods or services received did not qualify for recognition as assets.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2024-01-01
-Paragraph 51
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2024-en-r&anchor=para_51_a&doctype=Standard
-URIDate 2024-03-27

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

The number of shares issued by the entity.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2024-01-01
-Paragraph 106
-Subparagraph d
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2024-en-r&anchor=para_106_d&doctype=Standard
-URIDate 2024-03-27

Name:	ifrs-full_NumberOfSharesIssued
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

The proportion of the voting rights in a subsidiary held by the entity. [Refer: Total for all subsidiaries [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2024-01-01
-Paragraph 17
-Subparagraph b
-Clause iii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=27&code=ifrs-tx-2024-en-r&anchor=para_17_b_iii&doctype=Standard
-URIDate 2024-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2024-01-01
-Paragraph 16
-Subparagraph b
-Clause iii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=27&code=ifrs-tx-2024-en-r&anchor=para_16_b_iii&doctype=Standard
-URIDate 2024-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2024-01-01
-Paragraph 19B
-Subparagraph c
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2024-en-r&anchor=para_19B_c&doctype=Standard
-URIDate 2024-03-27

Name:	ifrs-full_ProportionOfVotingPowerHeldInSubsidiary
Namespace Prefix:	ifrs-full_
Data Type:	dtr-2022:percentItemType
Balance Type:	na
Period Type:	duration

The number of shares in the entity held by the entity or by its subsidiaries or associates. [Refer: Total for all associates [member]; Total for all subsidiaries [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2024-01-01
-Paragraph 79
-Subparagraph a
-Clause vi
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2024-en-r&anchor=para_79_a_vi&doctype=Standard
-URIDate 2024-03-27

Name:	ifrs-full_SharesInEntityHeldByEntityOrByItsSubsidiariesOrAssociates
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Name:	ifrs-full_ClassesOfEntitysOwnEquityInstrumentsAxis=fmst_ForemostWarrantMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_ClassesOfShareCapitalAxis=fmst_RioGrandeCommonShareMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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

Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=fmst_ForemostOption2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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

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

Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=fmst_ForemostRsu1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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

Name:	ifrs-full_BorrowingsByNameAxis=fmst_BarnardPromissoryNoteMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_BorrowingsByNameAxis=fmst_ForemostPromissoryNoteMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_CategoriesOfRelatedPartiesAxis=ifrs-full_KeyManagementPersonnelOfEntityOrParentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: