XML 61 R50.htm IDEA: XBRL DOCUMENT
v3.25.1

Note 3 - Loans Receivable and Allowance for Credit Losses - Loans - Schedule of Modified Financing Receivables (Details) - Commercial Real Estate Portfolio Segment [Member] - Commercial Loan [Member] - USD ($) $ in Thousands | 3 Months Ended
--- | ---
Mar. 31, 2025 | Mar. 31, 2024
Financing Receivable, Excluding Accrued Interest, Modified in Period, to Total Financing Receivables, Percentage | 0.70% | 0.60%
Extended Maturity [Member] |  |
Financing Receivable, Excluding Accrued Interest, Modified, Weighted Average Term Extension Payment Delay (Year) | 2 years 8 months 12 days | 1 year 8 months 12 days
Extended Maturity and Payment Delay [Member] |  |
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount | $ 1,196 | $ 1,102

X
- Definition Period of increase in weighted average maturity of financing receivable modified (excluding accrued interest) for debtor experiencing financial difficulty, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days + References No definition available. + Details
Name: | fsbw_FinancingReceivableExcludingAccruedInterestModifiedWeightedAverageTermExtensionPaymentDelay
Namespace Prefix: | fsbw_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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
- Definition Percentage, excluding accrued interest, of financing receivable modified during period for debtor experiencing financial difficulty to total financing receivables. + 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_FinancingReceivableModificationToTotalFinancingReceivablesExcludingAccruedInterestPercent
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

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

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

X
- Details
Name: | us-gaap_LoanRestructuringModificationAxis=us-gaap_ExtendedMaturityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LoanRestructuringModificationAxis=fsbw_ExtendedMaturityAndPaymentDelayMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |