    <SEC-DOCUMENT>0000708781-24-000072-index.html : 20240718
    <SEC-HEADER>0000708781-24-000072.hdr.sgml : 20240718
    <ACCEPTANCE-DATETIME>20240718090244
    ACCESSION NUMBER:		0000708781-24-000072
    CONFORMED SUBMISSION TYPE:	8-K
    PUBLIC DOCUMENT COUNT:		40
    CONFORMED PERIOD OF REPORT:	20240718
    ITEM INFORMATION:		Results of Operations and Financial Condition
    ITEM INFORMATION:		Other Events
    ITEM INFORMATION:		Financial Statements and Exhibits
    FILED AS OF DATE:		20240718
    DATE AS OF CHANGE:		20240718

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			CASS INFORMATION SYSTEMS INC
    		CENTRAL INDEX KEY:			0000708781
    		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-BUSINESS SERVICES, NEC [7389]
    		ORGANIZATION NAME:           	07 Trade & Services
    		IRS NUMBER:				431265338
    		STATE OF INCORPORATION:			MO
    		FISCAL YEAR END:			1231

    	FILING VALUES:
    		FORM TYPE:		8-K
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	000-20827
    		FILM NUMBER:		241123787

    	BUSINESS ADDRESS:
    		STREET 1:		12444 POWERSCOURT DRIVE
    		CITY:			ST. LOUIS
    		STATE:			MO
    		ZIP:			63131
    		BUSINESS PHONE:		314-506-5500

    	MAIL ADDRESS:
    		STREET 1:		12444 POWERSCOURT DRIVE
    		CITY:			ST. LOUIS
    		STATE:			MO
    		ZIP:			63131

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	CASS COMMERCIAL CORP
    		DATE OF NAME CHANGE:	19950518
    </SEC-HEADER>
    <DOCUMENT>
    <TYPE>8-K
    <SEQUENCE>1
    <FILENAME>cass-20240718.htm
    <DESCRIPTION>8-K
    <TEXT>
    Document 1 - file: cass-20240718.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-99.1
    <SEQUENCE>2
    <FILENAME>cass-20240630xexx991.htm
    <DESCRIPTION>EX-99.1
    <TEXT>
    Document 2 - file: cass-20240630xexx991.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-99.2
    <SEQUENCE>3
    <FILENAME>investorpresentationq220.htm
    <DESCRIPTION>EX-99.2
    <TEXT>
    Document 3 - file: investorpresentationq220.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.SCH
    <SEQUENCE>4
    <FILENAME>cass-20240718.xsd
    <DESCRIPTION>XBRL TAXONOMY EXTENSION SCHEMA DOCUMENT
    <TEXT>
    Document 4 - file: cass-20240718.xsd

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.LAB
    <SEQUENCE>5
    <FILENAME>cass-20240718_lab.xml
    <DESCRIPTION>XBRL TAXONOMY EXTENSION LABEL LINKBASE DOCUMENT
    <TEXT>
    Document 5 - file: cass-20240718_lab.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.PRE
    <SEQUENCE>6
    <FILENAME>cass-20240718_pre.xml
    <DESCRIPTION>XBRL TAXONOMY EXTENSION PRESENTATION LINKBASE DOCUMENT
    <TEXT>
    Document 6 - file: cass-20240718_pre.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>7
    <FILENAME>g19798g42m88.jpg
    <TEXT>
    Document 7 - file: g19798g42m88.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>8
    <FILENAME>investorpresentationq220001.jpg
    <TEXT>
    Document 8 - file: investorpresentationq220001.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>9
    <FILENAME>investorpresentationq220002.jpg
    <TEXT>
    Document 9 - file: investorpresentationq220002.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>10
    <FILENAME>investorpresentationq220003.jpg
    <TEXT>
    Document 10 - file: investorpresentationq220003.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>11
    <FILENAME>investorpresentationq220004.jpg
    <TEXT>
    Document 11 - file: investorpresentationq220004.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>12
    <FILENAME>investorpresentationq220005.jpg
    <TEXT>
    Document 12 - file: investorpresentationq220005.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>13
    <FILENAME>investorpresentationq220006.jpg
    <TEXT>
    Document 13 - file: investorpresentationq220006.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>14
    <FILENAME>investorpresentationq220007.jpg
    <TEXT>
    Document 14 - file: investorpresentationq220007.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>15
    <FILENAME>investorpresentationq220008.jpg
    <TEXT>
    Document 15 - file: investorpresentationq220008.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>16
    <FILENAME>investorpresentationq220009.jpg
    <TEXT>
    Document 16 - file: investorpresentationq220009.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>17
    <FILENAME>investorpresentationq220010.jpg
    <TEXT>
    Document 17 - file: investorpresentationq220010.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>18
    <FILENAME>investorpresentationq220011.jpg
    <TEXT>
    Document 18 - file: investorpresentationq220011.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>19
    <FILENAME>investorpresentationq220012.jpg
    <TEXT>
    Document 19 - file: investorpresentationq220012.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>20
    <FILENAME>investorpresentationq220013.jpg
    <TEXT>
    Document 20 - file: investorpresentationq220013.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>21
    <FILENAME>investorpresentationq220014.jpg
    <TEXT>
    Document 21 - file: investorpresentationq220014.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>22
    <FILENAME>investorpresentationq220015.jpg
    <TEXT>
    Document 22 - file: investorpresentationq220015.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>23
    <FILENAME>investorpresentationq220016.jpg
    <TEXT>
    Document 23 - file: investorpresentationq220016.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>24
    <FILENAME>investorpresentationq220017.jpg
    <TEXT>
    Document 24 - file: investorpresentationq220017.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>25
    <FILENAME>investorpresentationq220018.jpg
    <TEXT>
    Document 25 - file: investorpresentationq220018.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>26
    <FILENAME>investorpresentationq220019.jpg
    <TEXT>
    Document 26 - file: investorpresentationq220019.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>27
    <FILENAME>investorpresentationq220020.jpg
    <TEXT>
    Document 27 - file: investorpresentationq220020.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>28
    <FILENAME>investorpresentationq220021.jpg
    <TEXT>
    Document 28 - file: investorpresentationq220021.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>29
    <FILENAME>investorpresentationq220022.jpg
    <TEXT>
    Document 29 - file: investorpresentationq220022.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>30
    <FILENAME>investorpresentationq220023.jpg
    <TEXT>
    Document 30 - file: investorpresentationq220023.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>31
    <FILENAME>investorpresentationq220024.jpg
    <TEXT>
    Document 31 - file: investorpresentationq220024.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>33
    <FILENAME>R1.htm
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 33 - file: R1.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EXCEL
    <SEQUENCE>34
    <FILENAME>Financial_Report.xlsx
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 34 - file: Financial_Report.xlsx

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>35
    <FILENAME>Show.js
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 35 - file: Show.js

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>36
    <FILENAME>report.css
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 36 - file: report.css

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>38
    <FILENAME>FilingSummary.xml
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 38 - file: FilingSummary.html

    Document 38 - RAW XML: FilingSummary.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>JSON
    <SEQUENCE>40
    <FILENAME>MetaLinks.json
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 40 - file: MetaLinks.json

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>ZIP
    <SEQUENCE>41
    <FILENAME>0000708781-24-000072-xbrl.zip
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 41 - file: 0000708781-24-000072-xbrl.zip

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>42
    <FILENAME>cass-20240718_htm.xml
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 42 - file: cass-20240718_htm.html

    Document 42 - RAW XML: cass-20240718_htm.xml

    </DOCUMENT>
    </SEC-DOCUMENT>