Note 3 - Material Accounting Policy Information (Details Textual) - CAD ($) $ in Thousands	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2024
Statement Line Items [Line Items]
Allowance account for credit losses of financial assets at end of period	$ 0	$ 0	$ 0

Amount of allowance account for credit losses on financial assets.

No definition available.

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