0000860413 2026-05-21 2026-05-21 0000860413 1 2026-05-21 2026-05-21 0000860413 2 2026-05-21 2026-05-21 0000860413 3 2026-05-21 2026-05-21 0000860413 4 2026-05-21 2026-05-21 0000860413 5 2026-05-21 2026-05-21 0000860413 6 2026-05-21 2026-05-21 0000860413 7 2026-05-21 2026-05-21 iso4217:USD pure S-3 S-3ASR EX-FILING FEES 0000860413 FIRST INTERSTATE BANCSYSTEM INC N/A N/A S-3 FIRST INTERSTATE BANCSYSTEM INC false Equity Common Stock, par value $0.00001 per share true 0.0001381 false Equity Preferred Stock, par value $0.00001 per share true 0.0001381 false Equity Depository Shares true 0.0001381 false Debt Debt Securities true 0.0001381 false Other Warrants true 0.0001381 false Other Purchase Contracts true 0.0001381 false Other Units true 0.0001381 0.00 0.00 0.00 0.00 0.00 An indeterminate aggregate number and amount of the securities of each class is being registered as may from time to time be offered and sold at indeterminate prices hereunder. The proposed maximum aggregate offering price per security will be determined from time to time by the registrant in connection with offers and sales of securities registered hereunder. Separate consideration may or may not be received for securities that are issuable on exercise, conversion or exchange of securities registered hereunder or that are represented by depositary shares. This registration statement also covers an indeterminate number of additional securities which may be issued (i) from time to time upon exercise, conversion or exchange of securities being registered hereunder and (ii) pursuant to Rule 416 under the Securities Act of 1933, as amended (the "Securities Act"), in connection with any stock split, stock dividend, reclassifications or similar transactions. In reliance on Rule 456(b) and Rule 457(r) under the Securities Act, the registrant is deferring payment of all registration fees and will pay the registration fees subsequently on a "pay-as-you-go" basis. The registrant will calculate the registration fee applicable to an offer of securities pursuant to this registration statement based on the fee payment rate in effect on the date of such fee payment. See Note 1. Each depositary share will be evidenced by depositary receipts issued pursuant to a deposit agreement. In the event the registrant elects to offer to the public whole or fractional interests in shares of preferred stock registered hereunder, depositary receipts will be distributed to those persons purchasing such interests and such shares will be issued to the depositary under the deposit agreement. See also Note 1. May consist of one or more series of senior or subordinated debt. See also Note 1. Warrants represent rights to purchase debt securities, common stock, or preferred stock registered hereunder. See also Note 1. Purchase contracts may be issued separately or as part of units consisting of a purchase contract and any combination of shares of our common stock, preferred stock or depositary shares. See also Note 1. Any securities registered hereunder may be sold as units with other securities registered hereunder. Each unit will be issued under a unit agreement and will represent an interest in two or more securities, which may or may not be separable from one another. See also Note 1.