Wellington Management Group LLP Increases Stake in First Interstate BancSystem, Inc. to 4.0%

Wellington Management Group LLP, along with its affiliates Wellington Group Holdings LLP and Wellington Investment Advisors Holdings LLP, filed a Schedule 13G/A on May 15, 2026, regarding their holdings in First Interstate BancSystem, Inc. (FIBK). The filing reveals that as of March 31, 2026, the group beneficially owns 3,882,437 shares of FIBK common stock, representing a 4.0% ownership stake. This is an increase from a previously reported 0.0% position. The shares are held of record by various investment advisers owned by the parent holding company, including Wellington Management Company LLP. The filing indicates that the reporting persons have shared dispositive power over all 3,882,437 shares and shared voting power over 2,347,013 shares. The securities were acquired in the ordinary course of business and not for the purpose of changing or influencing the control of the issuer. This amendment reflects the group's continued investment management activities for its diverse client base.