Parent Directory| Name | Size | Last Modified |
|---|---|---|
 0000860413-26-000007-index-headers.html | 2026-01-28 16:10:13 | |
| 0000860413-26-000007-index.html | 2026-01-28 16:10:13 | |
| 0000860413-26-000007.txt | 2026-01-28 16:10:13 | |
 0000860413-26-000007-xbrl.zip | 63626 | 2026-01-28 16:10:13 |
| dec2025ip.htm | 39803 | 2026-01-28 16:10:13 |
 dec2025ip001.jpg | 139127 | 2026-01-28 16:10:13 |
 dec2025ip002.jpg | 283965 | 2026-01-28 16:10:13 |
 dec2025ip003.jpg | 116371 | 2026-01-28 16:10:13 |
 dec2025ip004.jpg | 94683 | 2026-01-28 16:10:13 |
 dec2025ip005.jpg | 125235 | 2026-01-28 16:10:13 |
 dec2025ip006.jpg | 177137 | 2026-01-28 16:10:13 |
 dec2025ip007.jpg | 184105 | 2026-01-28 16:10:13 |
 dec2025ip008.jpg | 79414 | 2026-01-28 16:10:13 |
 dec2025ip009.jpg | 106905 | 2026-01-28 16:10:13 |
 dec2025ip010.jpg | 83461 | 2026-01-28 16:10:13 |
 dec2025ip011.jpg | 106629 | 2026-01-28 16:10:13 |
 dec2025ip012.jpg | 141359 | 2026-01-28 16:10:13 |
 dec2025ip013.jpg | 87176 | 2026-01-28 16:10:13 |
 dec2025ip014.jpg | 93665 | 2026-01-28 16:10:13 |
 dec2025ip015.jpg | 99469 | 2026-01-28 16:10:13 |
 dec2025ip016.jpg | 85022 | 2026-01-28 16:10:13 |
 dec2025ip017.jpg | 99784 | 2026-01-28 16:10:13 |
 dec2025ip018.jpg | 107218 | 2026-01-28 16:10:13 |
 dec2025ip019.jpg | 277597 | 2026-01-28 16:10:13 |
 dec2025ip020.jpg | 112678 | 2026-01-28 16:10:13 |
 dec2025ip021.jpg | 106016 | 2026-01-28 16:10:13 |
| fibk-20251231x8kpr.htm | 951140 | 2026-01-28 16:10:13 |
| fibk-20260128.htm | 32472 | 2026-01-28 16:10:13 |
| fibk-20260128.xsd | 1773 | 2026-01-28 16:10:13 |
| fibk-20260128_htm.xml | 2723 | 2026-01-28 16:10:13 |
| fibk-20260128_lab.xml | 21885 | 2026-01-28 16:10:13 |
| fibk-20260128_pre.xml | 12502 | 2026-01-28 16:10:13 |
 fibslogo2linea04.jpg | 165531 | 2026-01-28 16:10:13 |
| FilingSummary.xml | 1618 | 2026-01-28 16:10:13 |
| MetaLinks.json | 16849 | 2026-01-28 16:10:13 |
| R1.htm | 38077 | 2026-01-28 16:10:13 |
| report.css | 2767 | 2026-01-28 16:10:13 |
| Show.js | 1085 | 2026-01-28 16:10:13 |