Cover |
Apr. 29, 2026 |
|---|---|
| Document Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Apr. 29, 2026 |
| Title of 12(b) Security | Common stock, $0.00001 par value |
| Trading Symbol | FIBK |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| City Area Code | (406) |
| Local Phone Number | 255-5311 |
| Central Index Key | 0000860413 |
| Amendment Flag | false |
| Entity Address, Postal Zip Code | 59101 |
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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 For the EDGAR submission types of Form 8-K: the date of the report, the date of the earliest event reported; for the EDGAR submission types of Form N-1A: the filing date; for all other submission types: the end of the reporting or transition period. The format of the date is YYYY-MM-DD. 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 Code for the postal or zip code 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 Local phone number for entity. No definition available.
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- Definition Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Title of a 12(b) registered security. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Name of the Exchange on which a security is registered. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as soliciting material pursuant to Rule 14a-12 under the Exchange Act. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Trading symbol of an instrument as listed on an exchange. No definition available.
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- Definition Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as written communications pursuant to Rule 425 under the Securities Act. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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