Condensed Financial Information (Parent Company Only) (Tables)

12 Months Ended

Dec. 31, 2021

Condensed Financial Information Disclosure [Abstract]

Schedule of Condensed Financial Statements

Following is condensed financial information of First Interstate BancSystem, Inc.

December 31,	2021		2020
Condensed balance sheets:
Cash and cash equivalents	$	181.1	$	123.2
Investment in bank subsidiary	1,948.9		1,986.6
Advances to subsidiaries, net	5.9		41.0
Other assets	63.2		61.3
Total assets	$	2,199.1	$	2,212.1
Other liabilities	$	26.8	$	66.7
Long-term debt	98.7		98.6
Subordinated debentures held by subsidiary trusts	87.0		87.0
Total liabilities	212.5		252.3
Stockholders’ equity	1,986.6		1,959.8
Total liabilities and stockholders’ equity	$	2,199.1	$	2,212.1

Years Ended December 31,	2021		2020		2019
Condensed statements of income:
Dividends from subsidiaries	$	160.0	$	130.0	$	178.0
Other interest income	—		0.1		0.3
Other income, primarily management fees from subsidiaries	41.3		28.7		25.9
Total income	201.3		158.8		204.2
Salaries and benefits	36.4		31.5		34.2
Interest expense	8.2		6.6		4.7
Acquisition related expenses	11.6		—		17.0
Other operating expenses, net	17.6		15.6		14.8
Total expenses	73.8		53.7		70.7
Earnings before income tax benefit	127.5		105.1		133.5
Income tax benefit	(7.6)		(6.1)		(11.9)
Income before undistributed earnings of subsidiaries	135.1		111.2		145.4
Undistributed earnings of subsidiaries	57.0		50.0		35.6
Net income	$	192.1	$	161.2	$	181.0

Years Ended December 31,	2021		2020		2019
Condensed statements of cash flows:
Cash flows from operating activities:
Net income	$	192.1	$	161.2	$	181.0
Adjustments to reconcile net income to cash provided by operating activities:
Undistributed earnings of subsidiaries	(57.0)		(50.0)		(35.6)
Stock-based compensation expense	8.9		7.5		8.0
Other, net	(3.2)		(13.6)		8.1
Net cash provided by operating activities	140.8		105.1		161.5
Cash flows from financing activities:
Net (decrease) increase in advances from subsidiaries	23.7		16.7		(6.6)
Proceeds from issuance of long-term debt	—		98.6		—
Proceeds from issuance of common stock, net of stock issuance costs	0.4		1.1		1.0
Purchase and retirement of common stock	(5.4)		(116.8)		(2.5)
Dividends paid to common stockholders	(101.6)		(128.6)		(79.2)
Net cash used in financing activities	(82.9)		(129.0)		(87.3)
Net change in cash and cash equivalents	57.9		(23.9)		74.2
Cash and cash equivalents, beginning of year	123.2		147.1		72.9
Cash and cash equivalents, end of year	$	181.1	$	123.2	$	147.1