First Interstate BancSystem, Inc. Schedule 13G/A amendment reports that Wellington-affiliated entities beneficially own 3,882,437 shares of Common Stock (CUSIP 32055Y201), representing 3.98% of the class as shown on the cover pages. The filing lists shared voting power of 2,347,013 and shared dispositive power of 3,882,437 and identifies the relevant Wellington entities and investment advisers.
Positive
None.
Negative
None.
Insights
Wellington reports a sub-5% passive stake with shared control metrics.
The filing shows Wellington-affiliated entities beneficially own 3,882,437 shares, equal to 3.98% of the class and reports shared voting power of 2,347,013.
Ownership is held of record for clients of multiple Wellington investment advisers; the filing identifies the parent/holding structure and controlling adviser entities. Subsequent filings would show any material changes to this passive position.
Key Figures
Beneficial ownership:3,882,437 sharesPercent of class:3.98%Shared voting power:2,347,013 shares+3 more
6 metrics
Beneficial ownership3,882,437 sharesreported beneficially owned on Schedule 13G/A
Percent of class3.98%percent of class reported in Item 4(b)
Shared voting power2,347,013 sharesshared voting power reported on cover pages
Shared dispositive power3,882,437 sharesshared dispositive power reported on cover pages
CUSIP32055Y201Common Stock CUSIP on cover and Item 2(d)
Signature date05/15/2026signature dates for the filing
"Amount beneficially owned: See the responses to Item 9"
Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.
Shared dispositive powerregulatory
"Shared Dispositive Power 3,882,437.00"
Schedule 13G/Aregulatory
"First Interstate BancSystem, Inc. Schedule 13G/A amendment"
A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.
Investment adviser (IA)regulatory
"Wellington Management Company LLP - IA"
An investment adviser (IA) is a person or firm that provides personalized guidance on buying, selling, or holding investments and often manages client portfolios for a fee. Investors should care because an IA has a legal duty to act in the client's best interest—think of them as a navigator who plans and steers your financial journey—so their advice, fee structure and potential conflicts can directly affect returns and financial risk.
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
(Amendment No. 1)
First Interstate BancSystem, Inc.
(Name of Issuer)
Common Stock
(Title of Class of Securities)
32055Y201
(CUSIP Number)
03/31/2026
(Date of Event Which Requires Filing of this Statement)
Check the appropriate box to designate the rule pursuant to which this Schedule is filed:
Rule 13d-1(b)
Rule 13d-1(c)
Rule 13d-1(d)
schemaVersion:
SCHEDULE 13G
CUSIP Number(s):
32055Y201
1
Names of Reporting Persons
Wellington Management Group LLP
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
MASSACHUSETTS
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
2,347,013.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
3,882,437.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
3,882,437.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
4.0 %
12
Type of Reporting Person (See Instructions)
HC
SCHEDULE 13G
CUSIP Number(s):
32055Y201
1
Names of Reporting Persons
Wellington Group Holdings LLP
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
2,347,013.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
3,882,437.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
3,882,437.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
4.0 %
12
Type of Reporting Person (See Instructions)
HC
SCHEDULE 13G
CUSIP Number(s):
32055Y201
1
Names of Reporting Persons
Wellington Investment Advisors Holdings LLP
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
2,347,013.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
3,882,437.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
3,882,437.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
4.0 %
12
Type of Reporting Person (See Instructions)
HC
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
First Interstate BancSystem, Inc.
(b)
Address of issuer's principal executive offices:
PO Box 30918, 401 North 31st Street, Billings MT 59101
Item 2.
(a)
Name of person filing:
Wellington Management Group LLP
Wellington Group Holdings LLP
Wellington Investment Advisors Holdings LLP
(b)
Address or principal business office or, if none, residence:
c/o Wellington Management Company LLP, 280 Congress Street, Boston MA 02210
(c)
Citizenship:
Wellington Management Group LLP - Massachusetts
Wellington Group Holdings LLP - Delaware
Wellington Investment Advisors Holdings LLP - Delaware
(d)
Title of class of securities:
Common Stock
(e)
CUSIP No.:
32055Y201
Item 3.
If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)
Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)
Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)
Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)
Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)
An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)
An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)
A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)
A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)
A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)
A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J),
please specify the type of institution:
(k)
Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.
Ownership
(a)
Amount beneficially owned:
See the responses to Item 9 on the attached cover pages.
(b)
Percent of class:
3.98 %
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
0
(ii) Shared power to vote or to direct the vote:
See the responses to Item 6 on the attached cover pages.
(iii) Sole power to dispose or to direct the disposition of:
0
(iv) Shared power to dispose or to direct the disposition of:
See the responses to Item 8 on the attached cover pages.
Item 5.
Ownership of 5 Percent or Less of a Class.
Ownership of 5 percent or less of a class
Item 6.
Ownership of more than 5 Percent on Behalf of Another Person.
If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required.
The securities as to which this Schedule is filed are owned of record by clients of one or more investment advisers identified in Item 7 directly or indirectly owned by Wellington Management Group LLP. Those clients have the right to receive, or the power to direct the receipt of, dividends from, or the proceeds from the sale of, such securities. No such client is known to have such right or power with respect to more than five percent of this class of securities, except as follows:
Not Applicable.
Item 7.
Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary.
Pursuant to the instructions in Item 7 of Schedule 13G, the following lists the identity and Item 3 classification of each relevant entity that beneficially owns shares of the security class being reported on this Schedule 13G.
Wellington Group Holdings LLP - HC
Wellington Investment Advisors LLP - HC
Wellington Management Global Holdings, Ltd. - HC
One or more of the following investment advisers (the "Wellington Investment Advisers"):
Wellington Management Company LLP - IA
Wellington Management Canada LLC - IA
Wellington Management Singapore Pte Ltd - IA
Wellington Management Hong Kong Ltd - IA
Wellington Management International Ltd - IA
Wellington Management Japan Pte Ltd - IA
Wellington Management Australia Pty Ltd - IA
The securities as to which this Schedule is filed by Wellington Management Group LLP, as parent holding company of certain holding companies and the Wellington Investment Advisers, are owned of record by clients of the Wellington Investment Advisers. Wellington Investment Advisors Holdings LLP controls directly, or indirectly through Wellington Management Global Holdings, Ltd., the Wellington Investment Advisers. Wellington Investment Advisors Holdings LLP is owned by Wellington Group Holdings LLP. Wellington Group Holdings LLP is owned by Wellington Management Group LLP.
Item 8.
Identification and Classification of Members of the Group.
Not Applicable
Item 9.
Notice of Dissolution of Group.
Not Applicable
Item 10.
Certifications:
By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.
SIGNATURE
After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.
What stake does Wellington Management report in FIBK?
Wellington-affiliated entities report beneficial ownership of 3,882,437 shares representing 3.98% of the class. The shares are held of record by clients of Wellington investment advisers and are reported as shared voting and dispositive holdings.
Which Wellington entities are named on the Schedule 13G/A for FIBK?
The filing names Wellington Management Group LLP, Wellington Group Holdings LLP, and Wellington Investment Advisors Holdings LLP. It also lists several Wellington investment advisers that hold the shares of record for clients.
How much voting power does Wellington report for FIBK shares?
The filing discloses shared voting power of 2,347,013 shares. Sole voting and sole dispositive power are reported as 0 for the named Wellington entities on the cover pages.
Does the Schedule 13G/A indicate Wellington controls the FIBK shares directly?
The filing states the shares are owned of record by clients of Wellington investment advisers and identifies Wellington entities in a parent/holding structure. It does not state direct sole control; the disclosure shows shared powers.
What CUSIP and class are covered in this filing for FIBK?
The Schedule 13G/A covers Common Stock with CUSIP 32055Y201. The cover pages and Item 4 tie the ownership figures to that class of securities.
