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v3.22.4

Subsequent Events (Details) - Forecast $ in Thousands | Mar. 31, 2023 USD ($)
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Subsequent Event [Line Items] |
Authorized repurchase | $ 15,000
Authorized repurchase, annual limitation | $ 5,000

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- Definition Stock Repurchase Program, Authorized Amount, Annual Limitation + References No definition available. + Details
Name: | fstr_StockRepurchaseProgramAuthorizedAmountAnnualLimitation
Namespace Prefix: | fstr_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Amount of stock repurchase plan authorized. + References No definition available. + Details
Name: | us-gaap_StockRepurchaseProgramAuthorizedAmount1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event. + References No definition available. + Details
Name: | us-gaap_SubsequentEventLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |