{
 "ok": true,
 "cik": "860413",
 "ticker": "FIBK",
 "name": "FIRST INTERSTATE BANCSYSTEM, INC.",
 "filings": [
  {
   "form": "8-K",
   "filed": "2026-09-16",
   "items": [
    "5.02 Departure or Election of Directors; Appointment of Officers",
    "9.01 Financial Statements and Exhibits"
   ],
   "url": "https://www.sec.gov/Archives/edgar/data/860413/000086041326000092/0000860413-26-000092-index.htm"
  },
  {
   "form": "8-K",
   "filed": "2026-08-21",
   "items": [
    "5.02 Departure or Election of Directors; Appointment of Officers",
    "9.01 Financial Statements and Exhibits"
   ],
   "url": "https://www.sec.gov/Archives/edgar/data/860413/000086041326000088/0000860413-26-000088-index.htm"
  },
  {
   "form": "10-Q",
   "filed": "2026-08-03",
   "items": [],
   "url": "https://www.sec.gov/Archives/edgar/data/860413/000086041326000084/0000860413-26-000084-index.htm"
  },
  {
   "form": "8-K",
   "filed": "2026-07-23",
   "items": [
    "2.02 Results of Operations and Financial Condition",
    "7.01 Regulation FD Disclosure",
    "8.01 Other Events",
    "9.01 Financial Statements and Exhibits"
   ],
   "url": "https://www.sec.gov/Archives/edgar/data/860413/000086041326000081/0000860413-26-000081-index.htm"
  },
  {
   "form": "8-K",
   "filed": "2026-07-16",
   "items": [
    "5.02 Departure or Election of Directors; Appointment of Officers",
    "9.01 Financial Statements and Exhibits"
   ],
   "url": "https://www.sec.gov/Archives/edgar/data/860413/000086041326000078/0000860413-26-000078-index.htm"
  },
  {
   "form": "8-K",
   "filed": "2026-07-09",
   "items": [
    "5.02 Departure or Election of Directors; Appointment of Officers",
    "9.01 Financial Statements and Exhibits"
   ],
   "url": "https://www.sec.gov/Archives/edgar/data/860413/000086041326000075/0000860413-26-000075-index.htm"
  }
 ],
 "events12m": 13,
 "sources": {
  "facts": "https://data.sec.gov/api/xbrl/companyfacts/CIK0000860413.json",
  "filings": "https://www.sec.gov/cgi-bin/browse-edgar?action=getcompany&CIK=860413"
 },
 "license": "Figures as filed with the SEC. Card text CC BY 4.0, POPS4.",
 "notAdvice": "Reporting, not investment advice. No price targets, no buy or sell views.",
 "edgar": "🫧 Edgar looked up FIRST INTERSTATE BANCSYSTEM, INC. ($FIBK). Last filing: 8-K (5.02 Departure or Election of Directors; Appointment of Officers), 2026-09-16. 13 event filings (8-K) in the past twelve months.",
 "auditor": {
  "changes": [],
  "nonReliance": [],
  "restatedSince": null
 },
 "edgarette": "🔖 The filings carry no annual revenue line Edgarette can read (common for banks and insurers, which report income differently). Nothing weighed, nothing guessed."
}