Document And Entity Information |
12 Months Ended |
|---|---|
Dec. 31, 2025 | |
| Document Information [Line Items] | |
| Document Type | S-4 |
| Entity Registrant Name | FS BANCORP, INC. |
| Entity Incorporation, State or Country Code | WA |
| Entity Tax Identification Number | 45-4585178 |
| Entity Address, Address Line One | 6920 220th Street SW |
| Entity Address, City or Town | Mountlake Terrace |
| Entity Address, State or Province | WA |
| Entity Address, Postal Zip Code | 98043 |
| City Area Code | 425 |
| Local Phone Number | 771-5299 |
| Entity Filer Category | Accelerated Filer |
| Entity Small Business | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001530249 |
| Amendment Flag | false |
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- Definition Boolean flag that is true when the XBRL content amends previously-filed or accepted submission. No definition available.
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- Definition Area code of city No definition available.
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
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- Definition The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word 'Other'. No definition available.
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- Definition Address Line 1 such as Attn, Building Name, Street Name No definition available.
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- Definition Name of the City or Town No definition available.
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- Definition Code for the postal or zip code No definition available.
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- Definition Name of the state or province. No definition available.
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- Definition A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Indicate if registrant meets the emerging growth company criteria. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Indicate whether the registrant is one of the following: Large Accelerated Filer, Accelerated Filer, Non-accelerated Filer. Definitions of these categories are stated in Rule 12b-2 of the Exchange Act. This information should be based on the registrant's current or most recent filing containing the related disclosure. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Two-character EDGAR code representing the state or country of incorporation. No definition available.
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- Definition The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Indicates that the company is a Smaller Reporting Company (SRC). Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition The Tax Identification Number (TIN), also known as an Employer Identification Number (EIN), is a unique 9-digit value assigned by the IRS. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Local phone number for entity. No definition available.
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