XML 107 R92.htm IDEA: XBRL DOCUMENT
v3.25.1

Note 10 - Employee Benefits (Details Textual) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage | 100.00% |  |
Defined Contribution Plan, Cost | $ 1.9 | $ 1.7 | $ 1.9
The 401K Plan One [Member] |  |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Match | 100.00% |  |
The 401K Plan One [Member] | Minimum [Member] |  |  |
Defined Contribution Plan, Contribution By Employee, Percent | 1.00% |  |
The 401K Plan One [Member] | Maximum [Member] |  |  |
Defined Contribution Plan, Contribution By Employee, Percent | 3.00% |  |
The 401K Plan Two [Member] |  |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Match | 50.00% |  |
The 401K Plan Two [Member] | Minimum [Member] |  |  |
Defined Contribution Plan, Contribution By Employee, Percent | 4.00% |  |
The 401K Plan Two [Member] | Maximum [Member] |  |  |
Defined Contribution Plan, Contribution By Employee, Percent | 5.00% |  |

X
- Definition Percentage of employee gross pay the employee may contribute to a defined contribution plan + References No definition available. + Details
Name: | fsbw_DefinedContributionPlanContributionByEmployeePercent
Namespace Prefix: | fsbw_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of cost for defined contribution plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 70 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480794/715-70-50-1 + Details
Name: | us-gaap_DefinedContributionPlanCostRecognized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Percentage employer matches of the employee's percentage contribution matched. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of employer's matching contributions to a defined contribution plan that vests in a given year. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployersMatchingContributionAnnualVestingPercentage
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_RetirementPlanNameAxis=fsbw_The401kPlanOneMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanNameAxis=fsbw_The401kPlanTwoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |