XML 66 R55.htm IDEA: XBRL DOCUMENT
v3.24.2.u1

Note 3 - Loans Receivable and Allowance for Credit Losses on Loans - Schedule of Past Due Loans (Details) - USD ($) $ in Thousands | Jun. 30, 2024 | Dec. 31, 2023
--- | --- | ---
Financing Receivable, before Allowance for Credit Loss |  | $ 2,488,422 | $ 2,433,015
Financing Receivable, Nonaccrual | [1] | 11,406 | 10,952
Real Estate Portfolio Segment [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 1,536,003 | 1,530,381
Financing Receivable, Nonaccrual | [1] | 6,179 | 6,056
Real Estate Portfolio Segment [Member] | Commercial Real Estate [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 359,404 | 366,328
Financing Receivable, Nonaccrual |  | 1,116 | 1,088
Real Estate Portfolio Segment [Member] | Construction Loans [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 274,209 | 303,054
Financing Receivable, Nonaccrual | [1] | 4,737 | 4,699
Real Estate Portfolio Segment [Member] | Home Equity Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 73,749 | 69,488
Financing Receivable, Nonaccrual | [1] | 156 | 173
Real Estate Portfolio Segment [Member] | One-to-four Family Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 588,966 | 567,742
Financing Receivable, Nonaccrual | [1] | 170 | 96
Real Estate Portfolio Segment [Member] | Multifamily [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 239,675 | 223,769
Financing Receivable, Nonaccrual | [1] | 0 | 0
Consumer Portfolio Segment [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 641,688 | 646,753
Financing Receivable, Nonaccrual | [1] | 2,652 | 2,213
Consumer Portfolio Segment [Member] | Indirect Home Improvement Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 563,621 | 569,903
Financing Receivable, Nonaccrual | [1] | 2,319 | 1,863
Consumer Portfolio Segment [Member] | Marine Loans [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 74,627 | 73,310
Financing Receivable, Nonaccrual | [1] | 327 | 342
Consumer Portfolio Segment [Member] | Other Consumer Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 3,440 | 3,540
Financing Receivable, Nonaccrual | [1] | 6 | 8
Commercial Business Portfolio Segment [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 310,731 | 255,881
Financing Receivable, Nonaccrual | [1] | 2,575 | 2,683
Commercial Business Portfolio Segment [Member] | Commercial And Industrial [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 285,183 | 238,301
Financing Receivable, Nonaccrual | [1] | 2,575 | 2,683
Commercial Business Portfolio Segment [Member] | Warehouse Lending Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 25,548 | 17,580
Financing Receivable, Nonaccrual | [1] | 0 | 0
Financial Asset, 30 to 59 Days Past Due [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 2,553 | 2,268
Financial Asset, 30 to 59 Days Past Due [Member] | Real Estate Portfolio Segment [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 102 | 79
Financial Asset, 30 to 59 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | Commercial Real Estate [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 0 | 0
Financial Asset, 30 to 59 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | Construction Loans [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 0 | 0
Financial Asset, 30 to 59 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | Home Equity Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 24 | 79
Financial Asset, 30 to 59 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | One-to-four Family Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 78 | 0
Financial Asset, 30 to 59 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | Multifamily [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 0 | 0
Financial Asset, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 2,451 | 2,189
Financial Asset, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Indirect Home Improvement Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 2,265 | 1,759
Financial Asset, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Marine Loans [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 181 | 373
Financial Asset, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Other Consumer Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 5 | 57
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Business Portfolio Segment [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 0 | 0
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Business Portfolio Segment [Member] | Commercial And Industrial [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 0 | 0
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Business Portfolio Segment [Member] | Warehouse Lending Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 0 | 0
Financial Asset, 60 to 89 Days Past Due [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 1,608 | 1,630
Financial Asset, 60 to 89 Days Past Due [Member] | Real Estate Portfolio Segment [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 323 | 121
Financial Asset, 60 to 89 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | Commercial Real Estate [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 323 | 0
Financial Asset, 60 to 89 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | Construction Loans [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 0 | 0
Financial Asset, 60 to 89 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | Home Equity Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 0 | 25
Financial Asset, 60 to 89 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | One-to-four Family Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 0 | 96
Financial Asset, 60 to 89 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | Multifamily [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 0 | 0
Financial Asset, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 1,285 | 1,509
Financial Asset, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Indirect Home Improvement Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 1,041 | 1,248
Financial Asset, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Marine Loans [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 239 | 243
Financial Asset, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Other Consumer Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 5 | 18
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Business Portfolio Segment [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 0 | 0
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Business Portfolio Segment [Member] | Commercial And Industrial [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 0 | 0
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Business Portfolio Segment [Member] | Warehouse Lending Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 0 | 0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 7,585 | 3,570
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Real Estate Portfolio Segment [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 4,893 | 136
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | Commercial Real Estate [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 0 | 0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | Construction Loans [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 4,737 | 0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | Home Equity Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 156 | 136
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | One-to-four Family Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 0 | 0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | Multifamily [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 0 | 0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 991 | 920
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Indirect Home Improvement Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 901 | 777
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Marine Loans [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 85 | 137
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Other Consumer Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 5 | 6
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Business Portfolio Segment [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 1,701 | 2,514
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Business Portfolio Segment [Member] | Commercial And Industrial [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 1,701 | 2,514
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Business Portfolio Segment [Member] | Warehouse Lending Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 0 | 0
Financial Asset, Past Due [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 11,746 | 7,468
Financial Asset, Past Due [Member] | Real Estate Portfolio Segment [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 5,318 | 336
Financial Asset, Past Due [Member] | Real Estate Portfolio Segment [Member] | Commercial Real Estate [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 323 | 0
Financial Asset, Past Due [Member] | Real Estate Portfolio Segment [Member] | Construction Loans [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 4,737 | 0
Financial Asset, Past Due [Member] | Real Estate Portfolio Segment [Member] | Home Equity Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 180 | 240
Financial Asset, Past Due [Member] | Real Estate Portfolio Segment [Member] | One-to-four Family Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 78 | 96
Financial Asset, Past Due [Member] | Real Estate Portfolio Segment [Member] | Multifamily [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 0 | 0
Financial Asset, Past Due [Member] | Consumer Portfolio Segment [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 4,727 | 4,618
Financial Asset, Past Due [Member] | Consumer Portfolio Segment [Member] | Indirect Home Improvement Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 4,207 | 3,784
Financial Asset, Past Due [Member] | Consumer Portfolio Segment [Member] | Marine Loans [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 505 | 753
Financial Asset, Past Due [Member] | Consumer Portfolio Segment [Member] | Other Consumer Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 15 | 81
Financial Asset, Past Due [Member] | Commercial Business Portfolio Segment [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 1,701 | 2,514
Financial Asset, Past Due [Member] | Commercial Business Portfolio Segment [Member] | Commercial And Industrial [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 1,701 | 2,514
Financial Asset, Past Due [Member] | Commercial Business Portfolio Segment [Member] | Warehouse Lending Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 0 | 0
Financial Asset, Not Past Due [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 2,476,676 | 2,425,547
Financial Asset, Not Past Due [Member] | Real Estate Portfolio Segment [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 1,530,685 | 1,530,045
Financial Asset, Not Past Due [Member] | Real Estate Portfolio Segment [Member] | Commercial Real Estate [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 359,081 | 366,328
Financial Asset, Not Past Due [Member] | Real Estate Portfolio Segment [Member] | Construction Loans [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 269,472 | 303,054
Financial Asset, Not Past Due [Member] | Real Estate Portfolio Segment [Member] | Home Equity Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 73,569 | 69,248
Financial Asset, Not Past Due [Member] | Real Estate Portfolio Segment [Member] | One-to-four Family Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 588,888 | 567,646
Financial Asset, Not Past Due [Member] | Real Estate Portfolio Segment [Member] | Multifamily [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 239,675 | 223,769
Financial Asset, Not Past Due [Member] | Consumer Portfolio Segment [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 636,961 | 642,135
Financial Asset, Not Past Due [Member] | Consumer Portfolio Segment [Member] | Indirect Home Improvement Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 559,414 | 566,119
Financial Asset, Not Past Due [Member] | Consumer Portfolio Segment [Member] | Marine Loans [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 74,122 | 72,557
Financial Asset, Not Past Due [Member] | Consumer Portfolio Segment [Member] | Other Consumer Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 3,425 | 3,459
Financial Asset, Not Past Due [Member] | Commercial Business Portfolio Segment [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 309,030 | 253,367
Financial Asset, Not Past Due [Member] | Commercial Business Portfolio Segment [Member] | Commercial And Industrial [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | 283,482 | 235,787
Financial Asset, Not Past Due [Member] | Commercial Business Portfolio Segment [Member] | Warehouse Lending Loan [Member] |  |  |
Financing Receivable, before Allowance for Credit Loss |  | $ 25,548 | $ 17,580
[1] | Includes loans less than 90 days past due as applicable.

X
- Definition Amortized cost of financing receivable on nonaccrual status. Excludes net investment in lease. + References Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 7 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481962/310-10-50-7 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph a -Subparagraph (3) -Publisher SEC Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph a -Subparagraph (2) -Publisher SEC Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 16 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-16 + Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost, before allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 13 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481990/310-10-45-13 Reference 2: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 7A -Publisher FASB -URI https://asc.fasb.org/1943274/2147481962/310-10-50-7A Reference 3: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 29 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481962/310-10-50-29 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph a -Subparagraph (1) -Publisher SEC Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph a -Subparagraph (2) -Publisher SEC Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef -Name Regulation S-K (SK) -Number 229 -Section 1404 -Paragraph a -Publisher SEC Reference 7: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 80 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-80 Reference 8: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479294/326-20-55-79 Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479344/326-20-45-1 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(3)(b)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 14 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-14 Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-5 + Details
Name: | us-gaap_NotesReceivableGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

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

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

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

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

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

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

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

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

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fsbw_OtherConsumerLoanMember
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: |

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

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

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_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancialAssetNotPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |