XML 62 R51.htm IDEA: XBRL DOCUMENT
v3.25.3

Note 3 - Loans Receivable and Allowance for Credit Losses - Loans - Schedule of Financing Receivable, Modified, Past Due (Details) $ in Thousands | 9 Months Ended
--- | ---
Sep. 30, 2025 USD ($)
Financial Asset, 30 to 59 Days Past Due [Member] |
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount | $ 0
Financial Asset, 60 to 89 Days Past Due [Member] |
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount | 0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] |
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount | 9,349
Financial Asset, Past Due [Member] |
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount | 9,349
Commercial and Speculative Construction and Development [Member] | Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member] |
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount | 0
Commercial and Speculative Construction and Development [Member] | Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member] |
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount | 0
Commercial and Speculative Construction and Development [Member] | Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] |
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount | 9,150
Commercial and Speculative Construction and Development [Member] | Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Past Due [Member] |
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount | 9,150
Commercial And Industrial [Member] | Commercial Business Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member] |
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount | 0
Commercial And Industrial [Member] | Commercial Business Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member] |
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount | 0
Commercial And Industrial [Member] | Commercial Business Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member] |
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount | 199
Commercial And Industrial [Member] | Commercial Business Portfolio Segment [Member] | Financial Asset, Past Due [Member] |
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount | $ 199

X
- Definition Amortized cost excluding accrued interest, of financing receivable modified during period for debtor experiencing financial difficulty. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 42 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481962/310-10-50-42 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestModifiedPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivables30To59DaysPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivables60To89DaysPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancialAssetPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fsbw_CommercialAndSpeculativeConstructionAndDevelopmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fsbw_CommercialAndIndustrialMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=fsbw_CommercialBusinessPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |