Capital Stock and Dividend Restrictions	12 Months Ended
Capital Stock and Dividend Restrictions	Dec. 31, 2025
Equity [Abstract]
Capital Stock and Dividend Restrictions	CAPITAL STOCK AND DIVIDEND RESTRICTIONS The Company’s common stock is traded on the NASDAQ stock market, or NASDAQ, under the symbol “FIBK.” As of December 31, 2025, the Company is authorized to issue an aggregate of 150,100,000 shares of capital stock, of which, 150,000,000 shares are designated as common stock, and 100,000 are designated as preferred stock. Our common stock is uncertificated and has one vote per share. The Company had 101,105,745 and 104,585,964 shares of common stock outstanding as of December 31, 2025 and 2024, respectively, and no shares of preferred stock outstanding as of December 31, 2025 and 2024. During 2025, the Company issued 39,058 shares of its common stock to directors for their annual service on the Company's Board. The aggregate value of the shares issued to directors of $1.1 million is amortized into stock-based compensation expense in the accompanying consolidated statements of changes in stockholders’ equity over a one-year service period. During 2024 and 2023, the Company issued 43,514 and 54,414 shares of its common stock with an aggregate value of $1.2 million and $1.2 million to directors for their service on the Company’s Board during 2024 and 2023, respectively. The aggregate value of the shares issued to directors is included in stock-based compensation expense in the accompanying consolidated statements of changes in stockholders’ equity. On August 28, 2025, the board of directors of the Company adopted a new stock repurchase program, pursuant to which the Company has been authorized to repurchase up to $150.0 million of its issued and outstanding shares of common stock on or prior to March 31, 2027, which is the expiration date of the program. On January 27, 2026, the board of directors authorized an increase to the repurchase program of an additional $150.0 million, or a total of $300.0 million since August 2025. Any repurchased shares will be returned to authorized but unissued shares of common stock, as permitted under applicable Delaware law. During 2025, 3,653,914 shares of common stock were repurchased under the stock repurchase program at a total cost of $117.6 million or at a weighted average price of $32.18 per share. As of December 31, 2025, following these repurchases, approximately $32.4 million remained available for future purchases under the program. Other stock repurchases during 2025 and 2024 were redemptions of vested restricted shares tendered in lieu of cash for payment of income tax withholding amounts by participants in the Company’s equity compensation plans. On May 25, 2023, the Company filed a Registration Statement on Form S-8 to register two million shares of common stock to be issued pursuant to the Company's 2023 Equity and Incentive Plan. On May 23, 2024, the Company filed a Registration Statement on Form S-8 to register an additional two million shares of common stock to be issued pursuant to the Company's 2023 Equity and Incentive Plan. On May 26, 2023, the Company filed a universal shelf registration statement on Form S-3, which was subsequently declared effective by the SEC. The shelf registration statement allows the Company to raise additional capital from time to time through offers and sales of registered securities consisting of debt securities, preferred stock, depository shares, common stock, warrants, purchase contracts, and units or units consisting of any combination of the foregoing securities. The Company may sell these securities using the prospectus in the shelf registration statement, together with applicable prospectus supplements, from time to time, in one or more offerings. The payment of dividends by subsidiary banks is subject to various federal and state regulatory limitations. In general, a bank is limited, without the prior consent of its regulators, to paying dividends that do not exceed current year net profits together with retained earnings from the two preceding calendar years. The Company’s debt instruments also include limitations on the payment of dividends.

The entire disclosure for equity.

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+ Details

FIRST INTERSTATE BANCSYSTEM INC 10-K