LIMITED POWER OF ATTORNEY FOR
SECTION 16 REPORTING OBLIGATIONS

The undersigned hereby makes, constitutes and appoints each of Terrill R. Moore
and Lyle R. Knight, each acting individually, as the undersigned's true and
lawful attorney-in-fact, with full power and authority as hereinafter described
on behalf of and in the name, place and stead of the undersigned to:
(1)	prepare, execute, acknowledge, deliver and file Forms 3, 4 and 5 (including
any amendments thereto) with respect to the securities of First Interstate
Bancsystem, Inc., a Montana corporation (the "Company"), with the United States
Securities and Exchange Commission, any national securities exchanges and the
Company, as considered necessary or advisable under Section 16(a) of the
Securities Exchange Act of 1934 and the rules and regulations promulgated
thereunder, as amended from time to time (the "Exchange Act");
(2)	seek or obtain, as the undersigned's representative and on the undersigned's
behalf, information on transactions in the Company's securities from any third
party, including brokers, employee benefit plan administrators and trustees, and
the undersigned hereby authorizes any such person to release any such
information to the undersigned and approves and ratifies any such release of
information; and
(3)	perform any and all other acts which in the discretion of such
attorney-in-fact are necessary or desirable for and on behalf of the undersigned
in connection with the foregoing.
The undersigned acknowledges that:
(1)	this Power of Attorney authorizes, but does not require, each such
attorney-in-fact to act in their discretion on information provided to such
attorney-in-fact without independent verification of such information;
(2)	any documents prepared and/or executed by either such attorney-in-fact on
behalf of the undersigned pursuant to this Power of Attorney will be in such
form and will contain such information and disclosure as such attorney-in-fact,
in his or her discretion, deems necessary or desirable;
(3)	neither the Company nor either of such attorneys-in-fact assumes (i) any
liability for the undersigned's responsibility to comply with the requirements
of the Exchange Act, (ii) any liability of the undersigned for any failure to
comply with such requirements, or (iii) any obligation or liability of the
undersigned for profit disgorgement under Section 16(b) of the Exchange Act; and
(4)	this Power of Attorney does not relieve the undersigned from responsibility
for compliance with the undersigned's obligations under the Exchange Act,
including without limitation the reporting requirements under Section 16 of the
Exchange Act.
The undersigned hereby gives and grants each of the foregoing attorneys-in-fact
full power and authority to do and perform all and every act and thing
whatsoever requisite, necessary or appropriate to be done in and about the
foregoing matters as fully to all intents and purposes as the undersigned might
or could do if present, hereby ratifying all that each such attorney-in-fact of,
for and on behalf of the undersigned, shall lawfully do or cause to be done by
virtue of this Limited Power of Attorney.
This Power of Attorney shall remain in full force and effect until revoked by
the undersigned in a signed writing delivered to each such attorney-in-fact.
IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of this 7th day of May, 2010.

/s/ JOHN M. HEYNEMAN
Signature

John M. Heyneman
Print Name

STATE OF MONTANA	)
	)
COUNTY OF YELLOWSTONE	)

On this 7th day of May, 2010, before me, the undersigned, a Notary Public for
the State of Montana, personally appeared John M. Heyneman and acknowledged that
he executed the within instrument.
IN WITNESS WHEREOF, I have hereunto set my hand and Official Seal the day and
year first above written.

(SEAL)	/s/ AMY ANDERSON
Print Name: Amy Anderson
Notary Public for the State of Montana
Residing at:  Billings, MT

My Commission Expires: 	December 15, 2013