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| 0000860413-20-000202-index.html | 2020-08-07 20:00:15 | |
| 0000860413-20-000202.txt | 2020-08-07 20:00:15 | |
 0000860413-20-000202-xbrl.zip | 492579 | 2020-08-07 20:00:15 |
| fibk-20200630.xsd | 70253 | 2020-08-07 20:00:15 |
| fibk-20200630x10q.htm | 4955822 | 2020-08-07 20:00:15 |
| fibk-20200630x10q_htm.xml | 5859425 | 2020-08-07 20:00:15 |
| fibk-20200630xex311.htm | 12227 | 2020-08-07 20:00:15 |
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| fibk-20200630xex32.htm | 4724 | 2020-08-07 20:00:15 |
| fibk-20200630_cal.xml | 175865 | 2020-08-07 20:00:15 |
| fibk-20200630_def.xml | 541378 | 2020-08-07 20:00:15 |
| fibk-20200630_lab.xml | 1179300 | 2020-08-07 20:00:15 |
| fibk-20200630_pre.xml | 737264 | 2020-08-07 20:00:15 |
| FilingSummary.xml | 42543 | 2020-08-07 20:00:15 |
| Financial_Report.xlsx | 164306 | 2020-08-07 20:00:15 |
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| report.css | 2767 | 2020-08-07 20:00:15 |
| Show.js | 1085 | 2020-08-07 20:00:15 |