Parent Directory| Name | Size | Last Modified |
|---|---|---|
 0000950170-23-018870-index-headers.html | 2023-05-08 16:42:43 | |
| 0000950170-23-018870-index.html | 2023-05-08 16:42:43 | |
| 0000950170-23-018870.txt | 2023-05-08 16:42:43 | |
 0000950170-23-018870-xbrl.zip | 466876 | 2023-05-08 16:42:43 |
| FilingSummary.xml | 72092 | 2023-05-08 16:42:43 |
| Financial_Report.xlsx | 163869 | 2023-05-08 16:42:43 |
| fisi-20230331.htm | 8848139 | 2023-05-08 16:42:43 |
| fisi-20230331.xsd | 95682 | 2023-05-08 16:42:43 |
| fisi-20230331_cal.xml | 111663 | 2023-05-08 16:42:43 |
| fisi-20230331_def.xml | 428253 | 2023-05-08 16:42:43 |
| fisi-20230331_htm.xml | 10931147 | 2023-05-08 16:42:43 |
| fisi-20230331_lab.xml | 761692 | 2023-05-08 16:42:43 |
| fisi-20230331_pre.xml | 658187 | 2023-05-08 16:42:43 |
| fisi-ex31_1.htm | 18834 | 2023-05-08 16:42:43 |
| fisi-ex31_2.htm | 18805 | 2023-05-08 16:42:43 |
| fisi-ex32.htm | 26450 | 2023-05-08 16:42:43 |
| MetaLinks.json | 1222997 | 2023-05-08 16:42:43 |
| R1.htm | 51557 | 2023-05-08 16:42:43 |
| R10.htm | 37399 | 2023-05-08 16:42:43 |
| R11.htm | 67015 | 2023-05-08 16:42:43 |
| R12.htm | 803035 | 2023-05-08 16:42:43 |
| R13.htm | 1918910 | 2023-05-08 16:42:43 |
| R14.htm | 116698 | 2023-05-08 16:42:43 |
| R15.htm | 94143 | 2023-05-08 16:42:43 |
| R16.htm | 74295 | 2023-05-08 16:42:43 |
| R17.htm | 190537 | 2023-05-08 16:42:43 |
| R18.htm | 81504 | 2023-05-08 16:42:43 |
| R19.htm | 340950 | 2023-05-08 16:42:43 |
| R2.htm | 91295 | 2023-05-08 16:42:43 |
| R20.htm | 54853 | 2023-05-08 16:42:43 |
| R21.htm | 42529 | 2023-05-08 16:42:43 |
| R22.htm | 41717 | 2023-05-08 16:42:43 |
| R23.htm | 634053 | 2023-05-08 16:42:43 |
| R24.htm | 167939 | 2023-05-08 16:42:43 |
| R25.htm | 6672 | 2023-05-08 16:42:43 |
| R26.htm | 54854 | 2023-05-08 16:42:43 |
| R27.htm | 30904 | 2023-05-08 16:42:43 |
| R28.htm | 24475 | 2023-05-08 16:42:43 |
| R29.htm | 67935 | 2023-05-08 16:42:43 |
| R3.htm | 34657 | 2023-05-08 16:42:43 |
| R30.htm | 774115 | 2023-05-08 16:42:43 |
| R31.htm | 1906032 | 2023-05-08 16:42:43 |
| R32.htm | 114332 | 2023-05-08 16:42:43 |
| R33.htm | 95949 | 2023-05-08 16:42:43 |
| R34.htm | 73447 | 2023-05-08 16:42:43 |
| R35.htm | 183277 | 2023-05-08 16:42:43 |
| R36.htm | 74137 | 2023-05-08 16:42:43 |
| R37.htm | 342075 | 2023-05-08 16:42:43 |
| R38.htm | 46811 | 2023-05-08 16:42:43 |
| R39.htm | 36346 | 2023-05-08 16:42:43 |
| R4.htm | 120331 | 2023-05-08 16:42:43 |
| R40.htm | 29432 | 2023-05-08 16:42:43 |
| R41.htm | 611313 | 2023-05-08 16:42:43 |
| R42.htm | 162930 | 2023-05-08 16:42:43 |
| R43.htm | 14149 | 2023-05-08 16:42:43 |
| R44.htm | 4956 | 2023-05-08 16:42:43 |
| R45.htm | 28721 | 2023-05-08 16:42:43 |
| R46.htm | 7476 | 2023-05-08 16:42:43 |
| R47.htm | 37604 | 2023-05-08 16:42:43 |
| R48.htm | 6843 | 2023-05-08 16:42:43 |
| R49.htm | 69980 | 2023-05-08 16:42:43 |
| R5.htm | 32561 | 2023-05-08 16:42:43 |
| R50.htm | 45652 | 2023-05-08 16:42:43 |
| R51.htm | 58190 | 2023-05-08 16:42:43 |
| R52.htm | 59163 | 2023-05-08 16:42:43 |
| R53.htm | 31564 | 2023-05-08 16:42:43 |
| R54.htm | 19929 | 2023-05-08 16:42:43 |
| R55.htm | 73365 | 2023-05-08 16:42:43 |
| R56.htm | 21579 | 2023-05-08 16:42:43 |
| R57.htm | 6744 | 2023-05-08 16:42:43 |
| R58.htm | 42261 | 2023-05-08 16:42:43 |
| R59.htm | 15290 | 2023-05-08 16:42:43 |
| R6.htm | 52132 | 2023-05-08 16:42:43 |
| R60.htm | 72351 | 2023-05-08 16:42:43 |
| R61.htm | 87710 | 2023-05-08 16:42:43 |
| R62.htm | 35018 | 2023-05-08 16:42:43 |
| R63.htm | 12297 | 2023-05-08 16:42:43 |
| R64.htm | 15377 | 2023-05-08 16:42:43 |
| R65.htm | 18462 | 2023-05-08 16:42:43 |
| R66.htm | 21223 | 2023-05-08 16:42:43 |
| R67.htm | 9218 | 2023-05-08 16:42:43 |
| R68.htm | 13534 | 2023-05-08 16:42:43 |
| R69.htm | 14135 | 2023-05-08 16:42:43 |
| R7.htm | 10487 | 2023-05-08 16:42:43 |
| R70.htm | 19498 | 2023-05-08 16:42:43 |
| R71.htm | 29236 | 2023-05-08 16:42:43 |
| R72.htm | 13895 | 2023-05-08 16:42:43 |
| R73.htm | 8703 | 2023-05-08 16:42:43 |
| R74.htm | 44966 | 2023-05-08 16:42:43 |
| R75.htm | 7411 | 2023-05-08 16:42:43 |
| R76.htm | 15284 | 2023-05-08 16:42:43 |
| R77.htm | 19403 | 2023-05-08 16:42:43 |
| R78.htm | 12567 | 2023-05-08 16:42:43 |
| R79.htm | 48688 | 2023-05-08 16:42:43 |
| R8.htm | 84378 | 2023-05-08 16:42:43 |
| R80.htm | 32697 | 2023-05-08 16:42:43 |
| R81.htm | 55968 | 2023-05-08 16:42:43 |
| R82.htm | 8932 | 2023-05-08 16:42:43 |
| R83.htm | 26319 | 2023-05-08 16:42:43 |
| R84.htm | 11135 | 2023-05-08 16:42:43 |
| R85.htm | 23821 | 2023-05-08 16:42:43 |
| R86.htm | 5588 | 2023-05-08 16:42:43 |
| R87.htm | 9338 | 2023-05-08 16:42:43 |
| R88.htm | 6744 | 2023-05-08 16:42:43 |
| R89.htm | 10307 | 2023-05-08 16:42:43 |
| R9.htm | 47386 | 2023-05-08 16:42:43 |
| R90.htm | 69733 | 2023-05-08 16:42:43 |
| R91.htm | 15746 | 2023-05-08 16:42:43 |
| R92.htm | 33629 | 2023-05-08 16:42:43 |
| R93.htm | 68997 | 2023-05-08 16:42:43 |
| R94.htm | 4327 | 2023-05-08 16:42:43 |
| R95.htm | 25875 | 2023-05-08 16:42:43 |
| R96.htm | 39915 | 2023-05-08 16:42:43 |
| report.css | 2768 | 2023-05-08 16:42:43 |
| Show.js | 1086 | 2023-05-08 16:42:43 |