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Namespace Prefix:	fstr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Number of Post-retirement Benefit Plan

No definition available.

Name:	fstr_NumberOfPostRetirementBenefitPlan
Namespace Prefix:	fstr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

Name:	fstr_NumberOfRetirementPlans
Namespace Prefix:	fstr_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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-Publisher FASB
-Name Accounting Standards Codification
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Name:	us-gaap_DefinedBenefitPlanContributionsByEmployer
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

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.

No definition available.

Name:	us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of contributions expected to be received by defined benefit plan from employer in next fiscal year following latest fiscal year.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of contributions expected to be received by defined benefit plan from employer in fiscal year. Excludes contributions paid by employer in current fiscal year.

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