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Leases - Narrative (Details) | 12 Months Ended
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Dec. 31, 2023
Lessee, Lease, Description |
Lessee lease renewal term | 12 years
Lessee, lease, termination period | 1 year
Minimum |
Lessee, Lease, Description |
Lessee remaining lease term | 2 years
Maximum |
Lessee, Lease, Description |
Lessee remaining lease term | 12 years

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- Definition Lessee, Lease, Renewal Term + References No definition available. + Details
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Namespace Prefix: | fstr_
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Balance Type: | na
Period Type: | duration

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- Definition Lessee, Lease, Termination Period + References No definition available. + Details
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Namespace Prefix: | fstr_
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- Definition Lessee, Remaining Lease Term + References No definition available. + Details
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Namespace Prefix: | fstr_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org//1943274/2147478964/842-20-50-3 + Details
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Balance Type: | na
Period Type: | duration

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- Details
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- Details
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Balance Type: |
Period Type: |