    <SEC-DOCUMENT>0000950170-25-060615-index.html : 20250430
    <SEC-HEADER>0000950170-25-060615.hdr.sgml : 20250430
    <ACCEPTANCE-DATETIME>20250430090738
    ACCESSION NUMBER:		0000950170-25-060615
    CONFORMED SUBMISSION TYPE:	8-K
    PUBLIC DOCUMENT COUNT:		55
    CONFORMED PERIOD OF REPORT:	20250430
    ITEM INFORMATION:		Regulation FD Disclosure
    ITEM INFORMATION:		Financial Statements and Exhibits
    FILED AS OF DATE:		20250430
    DATE AS OF CHANGE:		20250430

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			FIRST BUSINESS FINANCIAL SERVICES, INC.
    		CENTRAL INDEX KEY:			0001521951
    		STANDARD INDUSTRIAL CLASSIFICATION:	STATE COMMERCIAL BANKS [6022]
    		ORGANIZATION NAME:           	02 Finance
    		EIN:				391576570
    		STATE OF INCORPORATION:			WI
    		FISCAL YEAR END:			1231

    	FILING VALUES:
    		FORM TYPE:		8-K
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	001-34095
    		FILM NUMBER:		25891330

    	BUSINESS ADDRESS:
    		STREET 1:		401 CHARMANY DRIVE
    		CITY:			MADISON
    		STATE:			WI
    		ZIP:			53719
    		BUSINESS PHONE:		608-238-8008

    	MAIL ADDRESS:
    		STREET 1:		401 CHARMANY DRIVE
    		STREET 2:		PO BOX 44961
    		CITY:			MADISON
    		STATE:			WI
    		ZIP:			53744

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	First Business Financial Services, Inc.
    		DATE OF NAME CHANGE:	20110527
    </SEC-HEADER>
    <DOCUMENT>
    <TYPE>8-K
    <SEQUENCE>1
    <FILENAME>fbiz-20250430.htm
    <DESCRIPTION>8-K
    <TEXT>
    Document 1 - file: fbiz-20250430.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>8-K
    <SEQUENCE>2
    <FILENAME>fbiz-q1_2025_ip_8-k.pdf
    <DESCRIPTION>COURTESY COPY OF Q1_2025_IP_8-K
    <TEXT>
    Document 2 - file: fbiz-q1_2025_ip_8-k.pdf

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-99.1
    <SEQUENCE>3
    <FILENAME>fbiz-ex99_1.htm
    <DESCRIPTION>EX-99.1
    <TEXT>
    Document 3 - file: fbiz-ex99_1.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>4
    <FILENAME>fbiz-ex99_1s1.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 4 - file: fbiz-ex99_1s1.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>5
    <FILENAME>fbiz-ex99_1s2.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 5 - file: fbiz-ex99_1s2.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>6
    <FILENAME>fbiz-ex99_1s3.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 6 - file: fbiz-ex99_1s3.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>7
    <FILENAME>fbiz-ex99_1s4.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 7 - file: fbiz-ex99_1s4.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>8
    <FILENAME>fbiz-ex99_1s5.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 8 - file: fbiz-ex99_1s5.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>9
    <FILENAME>fbiz-ex99_1s6.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 9 - file: fbiz-ex99_1s6.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>10
    <FILENAME>fbiz-ex99_1s7.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 10 - file: fbiz-ex99_1s7.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>11
    <FILENAME>fbiz-ex99_1s8.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 11 - file: fbiz-ex99_1s8.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>12
    <FILENAME>fbiz-ex99_1s9.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 12 - file: fbiz-ex99_1s9.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>13
    <FILENAME>fbiz-ex99_1s10.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 13 - file: fbiz-ex99_1s10.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>14
    <FILENAME>fbiz-ex99_1s11.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 14 - file: fbiz-ex99_1s11.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>15
    <FILENAME>fbiz-ex99_1s12.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 15 - file: fbiz-ex99_1s12.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>16
    <FILENAME>fbiz-ex99_1s13.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 16 - file: fbiz-ex99_1s13.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>17
    <FILENAME>fbiz-ex99_1s14.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 17 - file: fbiz-ex99_1s14.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>18
    <FILENAME>fbiz-ex99_1s15.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 18 - file: fbiz-ex99_1s15.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>19
    <FILENAME>fbiz-ex99_1s16.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 19 - file: fbiz-ex99_1s16.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>20
    <FILENAME>fbiz-ex99_1s17.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 20 - file: fbiz-ex99_1s17.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>21
    <FILENAME>fbiz-ex99_1s18.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 21 - file: fbiz-ex99_1s18.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>22
    <FILENAME>fbiz-ex99_1s19.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 22 - file: fbiz-ex99_1s19.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>23
    <FILENAME>fbiz-ex99_1s20.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 23 - file: fbiz-ex99_1s20.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>24
    <FILENAME>fbiz-ex99_1s21.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 24 - file: fbiz-ex99_1s21.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>25
    <FILENAME>fbiz-ex99_1s22.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 25 - file: fbiz-ex99_1s22.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>26
    <FILENAME>fbiz-ex99_1s23.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 26 - file: fbiz-ex99_1s23.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>27
    <FILENAME>fbiz-ex99_1s24.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 27 - file: fbiz-ex99_1s24.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>28
    <FILENAME>fbiz-ex99_1s25.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 28 - file: fbiz-ex99_1s25.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>29
    <FILENAME>fbiz-ex99_1s26.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 29 - file: fbiz-ex99_1s26.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>30
    <FILENAME>fbiz-ex99_1s27.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 30 - file: fbiz-ex99_1s27.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>31
    <FILENAME>fbiz-ex99_1s28.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 31 - file: fbiz-ex99_1s28.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>32
    <FILENAME>fbiz-ex99_1s29.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 32 - file: fbiz-ex99_1s29.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>33
    <FILENAME>fbiz-ex99_1s30.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 33 - file: fbiz-ex99_1s30.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>34
    <FILENAME>fbiz-ex99_1s31.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 34 - file: fbiz-ex99_1s31.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>35
    <FILENAME>fbiz-ex99_1s32.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 35 - file: fbiz-ex99_1s32.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>36
    <FILENAME>fbiz-ex99_1s33.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 36 - file: fbiz-ex99_1s33.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>37
    <FILENAME>fbiz-ex99_1s34.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 37 - file: fbiz-ex99_1s34.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>38
    <FILENAME>fbiz-ex99_1s35.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 38 - file: fbiz-ex99_1s35.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>39
    <FILENAME>fbiz-ex99_1s36.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 39 - file: fbiz-ex99_1s36.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>40
    <FILENAME>fbiz-ex99_1s37.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 40 - file: fbiz-ex99_1s37.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>41
    <FILENAME>fbiz-ex99_1s38.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 41 - file: fbiz-ex99_1s38.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>42
    <FILENAME>fbiz-ex99_1s39.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 42 - file: fbiz-ex99_1s39.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>43
    <FILENAME>fbiz-ex99_1s40.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 43 - file: fbiz-ex99_1s40.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>44
    <FILENAME>fbiz-ex99_1s41.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 44 - file: fbiz-ex99_1s41.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>45
    <FILENAME>fbiz-ex99_1s42.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 45 - file: fbiz-ex99_1s42.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.SCH
    <SEQUENCE>46
    <FILENAME>fbiz-20250430.xsd
    <DESCRIPTION>XBRL TAXONOMY EXTENSION SCHEMA WITH EMBEDDED LINKBASES DOCUMENT
    <TEXT>
    Document 46 - file: fbiz-20250430.xsd

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>48
    <FILENAME>R1.htm
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 48 - file: R1.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EXCEL
    <SEQUENCE>49
    <FILENAME>Financial_Report.xlsx
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 49 - file: Financial_Report.xlsx

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>50
    <FILENAME>Show.js
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 50 - file: Show.js

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>51
    <FILENAME>report.css
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 51 - file: report.css

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>53
    <FILENAME>FilingSummary.xml
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 53 - file: FilingSummary.html

    Document 53 - RAW XML: FilingSummary.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>JSON
    <SEQUENCE>55
    <FILENAME>MetaLinks.json
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 55 - file: MetaLinks.json

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>ZIP
    <SEQUENCE>56
    <FILENAME>0000950170-25-060615-xbrl.zip
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 56 - file: 0000950170-25-060615-xbrl.zip

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>57
    <FILENAME>fbiz-20250430_htm.xml
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 57 - file: fbiz-20250430_htm.html

    Document 57 - RAW XML: fbiz-20250430_htm.xml

    </DOCUMENT>
    </SEC-DOCUMENT>