Parent Directory| Name | Size | Last Modified |
|---|---|---|
 0000860413-16-000043-index-headers.html | 2016-05-06 16:12:49 | |
| 0000860413-16-000043-index.html | 2016-05-06 16:12:49 | |
| 0000860413-16-000043.txt | 2016-05-06 16:12:49 | |
 0000860413-16-000043-xbrl.zip | 343822 | 2016-05-06 16:12:49 |
| fibk-20160331.xml | 4093647 | 2016-05-06 16:12:49 |
| fibk-20160331.xsd | 59650 | 2016-05-06 16:12:49 |
| fibk-20160331x10q.htm | 2233374 | 2016-05-06 16:12:49 |
| fibk-20160331xex103.htm | 83428 | 2016-05-06 16:12:49 |
| fibk-20160331xex311.htm | 12086 | 2016-05-06 16:12:49 |
| fibk-20160331xex312.htm | 12431 | 2016-05-06 16:12:49 |
| fibk-20160331xex32.htm | 4948 | 2016-05-06 16:12:49 |
| fibk-20160331_cal.xml | 148666 | 2016-05-06 16:12:49 |
| fibk-20160331_def.xml | 499111 | 2016-05-06 16:12:49 |
| fibk-20160331_lab.xml | 942678 | 2016-05-06 16:12:49 |
| fibk-20160331_pre.xml | 590997 | 2016-05-06 16:12:49 |
| FilingSummary.xml | 35295 | 2016-05-06 16:12:49 |
| Financial_Report.xlsx | 102412 | 2016-05-06 16:12:49 |
| R1.htm | 21103 | 2016-05-06 16:12:49 |
| R10.htm | 7660 | 2016-05-06 16:12:49 |
| R11.htm | 241445 | 2016-05-06 16:12:49 |
| R12.htm | 485277 | 2016-05-06 16:12:49 |
| R13.htm | 126811 | 2016-05-06 16:12:49 |
| R14.htm | 19472 | 2016-05-06 16:12:49 |
| R15.htm | 110240 | 2016-05-06 16:12:49 |
| R16.htm | 12416 | 2016-05-06 16:12:49 |
| R17.htm | 21681 | 2016-05-06 16:12:49 |
| R18.htm | 136361 | 2016-05-06 16:12:49 |
| R19.htm | 8590 | 2016-05-06 16:12:49 |
| R2.htm | 98953 | 2016-05-06 16:12:49 |
| R20.htm | 7354 | 2016-05-06 16:12:49 |
| R21.htm | 60200 | 2016-05-06 16:12:49 |
| R22.htm | 270769 | 2016-05-06 16:12:49 |
| R23.htm | 28592 | 2016-05-06 16:12:49 |
| R24.htm | 6324 | 2016-05-06 16:12:49 |
| R25.htm | 242239 | 2016-05-06 16:12:49 |
| R26.htm | 479001 | 2016-05-06 16:12:49 |
| R27.htm | 123402 | 2016-05-06 16:12:49 |
| R28.htm | 16678 | 2016-05-06 16:12:49 |
| R29.htm | 55955 | 2016-05-06 16:12:49 |
| R3.htm | 15560 | 2016-05-06 16:12:49 |
| R30.htm | 17551 | 2016-05-06 16:12:49 |
| R31.htm | 132041 | 2016-05-06 16:12:49 |
| R32.htm | 60198 | 2016-05-06 16:12:49 |
| R33.htm | 254167 | 2016-05-06 16:12:49 |
| R34.htm | 32145 | 2016-05-06 16:12:49 |
| R35.htm | 61428 | 2016-05-06 16:12:49 |
| R36.htm | 6593 | 2016-05-06 16:12:49 |
| R37.htm | 68786 | 2016-05-06 16:12:49 |
| R38.htm | 63690 | 2016-05-06 16:12:49 |
| R39.htm | 42039 | 2016-05-06 16:12:49 |
| R4.htm | 100822 | 2016-05-06 16:12:49 |
| R40.htm | 11852 | 2016-05-06 16:12:49 |
| R41.htm | 13592 | 2016-05-06 16:12:49 |
| R42.htm | 155567 | 2016-05-06 16:12:49 |
| R43.htm | 74538 | 2016-05-06 16:12:49 |
| R44.htm | 29130 | 2016-05-06 16:12:49 |
| R45.htm | 103864 | 2016-05-06 16:12:49 |
| R46.htm | 70924 | 2016-05-06 16:12:49 |
| R47.htm | 16986 | 2016-05-06 16:12:49 |
| R48.htm | 36077 | 2016-05-06 16:12:49 |
| R49.htm | 16265 | 2016-05-06 16:12:49 |
| R5.htm | 31749 | 2016-05-06 16:12:49 |
| R50.htm | 34987 | 2016-05-06 16:12:49 |
| R51.htm | 81224 | 2016-05-06 16:12:49 |
| R52.htm | 7410 | 2016-05-06 16:12:49 |
| R53.htm | 6192 | 2016-05-06 16:12:49 |
| R54.htm | 9631 | 2016-05-06 16:12:49 |
| R55.htm | 55149 | 2016-05-06 16:12:49 |
| R56.htm | 14592 | 2016-05-06 16:12:49 |
| R57.htm | 128159 | 2016-05-06 16:12:49 |
| R58.htm | 38862 | 2016-05-06 16:12:49 |
| R59.htm | 80414 | 2016-05-06 16:12:49 |
| R6.htm | 45711 | 2016-05-06 16:12:49 |
| R60.htm | 17700 | 2016-05-06 16:12:49 |
| R7.htm | 22943 | 2016-05-06 16:12:49 |
| R8.htm | 119415 | 2016-05-06 16:12:49 |
| R9.htm | 8468 | 2016-05-06 16:12:49 |
| report.css | 2767 | 2016-05-06 16:12:49 |
| Show.js | 1410 | 2016-05-06 16:12:49 |