    <SEC-DOCUMENT>0000842517-25-000071-index.html : 20250325
    <SEC-HEADER>0000842517-25-000071.hdr.sgml : 20250325
    <ACCEPTANCE-DATETIME>20250325085318
    ACCESSION NUMBER:		0000842517-25-000071
    CONFORMED SUBMISSION TYPE:	DEF 14A
    PUBLIC DOCUMENT COUNT:		20
    CONFORMED PERIOD OF REPORT:	20250506
    FILED AS OF DATE:		20250325
    DATE AS OF CHANGE:		20250325

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			ISABELLA BANK Corp
    		CENTRAL INDEX KEY:			0000842517
    		STANDARD INDUSTRIAL CLASSIFICATION:	STATE COMMERCIAL BANKS [6022]
    		ORGANIZATION NAME:           	02 Finance
    		EIN:				382830092
    		STATE OF INCORPORATION:			MI
    		FISCAL YEAR END:			1231

    	FILING VALUES:
    		FORM TYPE:		DEF 14A
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	000-18415
    		FILM NUMBER:		25766031

    	BUSINESS ADDRESS:
    		STREET 1:		401 NORTH MAIN STREET
    		CITY:			MT PLEASANT
    		STATE:			MI
    		ZIP:			48858
    		BUSINESS PHONE:		9897729471

    	MAIL ADDRESS:
    		STREET 1:		401 NORTH MAIN STREET
    		CITY:			MT PLEASANT
    		STATE:			MI
    		ZIP:			48858

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	ISABELLA BANK CORP
    		DATE OF NAME CHANGE:	20080602

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	IBT BANCORP INC /MI/
    		DATE OF NAME CHANGE:	19920703
    </SEC-HEADER>
    <DOCUMENT>
    <TYPE>DEF 14A
    <SEQUENCE>1
    <FILENAME>isba-20250320.htm
    <DESCRIPTION>DEF 14A
    <TEXT>
    Document 1 - file: isba-20250320.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.SCH
    <SEQUENCE>2
    <FILENAME>isba-20250320.xsd
    <DESCRIPTION>XBRL TAXONOMY EXTENSION SCHEMA DOCUMENT
    <TEXT>
    Document 2 - file: isba-20250320.xsd

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.LAB
    <SEQUENCE>3
    <FILENAME>isba-20250320_lab.xml
    <DESCRIPTION>XBRL TAXONOMY EXTENSION LABEL LINKBASE DOCUMENT
    <TEXT>
    Document 3 - file: isba-20250320_lab.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.PRE
    <SEQUENCE>4
    <FILENAME>isba-20250320_pre.xml
    <DESCRIPTION>XBRL TAXONOMY EXTENSION PRESENTATION LINKBASE DOCUMENT
    <TEXT>
    Document 4 - file: isba-20250320_pre.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>5
    <FILENAME>isba-20250320_g1.jpg
    <DESCRIPTION>ISBA LOGO
    <TEXT>
    Document 5 - file: isba-20250320_g1.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>6
    <FILENAME>isba-20250320_g2.jpg
    <DESCRIPTION>SIGNATURE
    <TEXT>
    Document 6 - file: isba-20250320_g2.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>7
    <FILENAME>isba-20250320_g3.jpg
    <DESCRIPTION>VOTING
    <TEXT>
    Document 7 - file: isba-20250320_g3.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>8
    <FILENAME>isba-20250320_g4.jpg
    <DESCRIPTION>CHART
    <TEXT>
    Document 8 - file: isba-20250320_g4.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>9
    <FILENAME>isba-20250320_g5.jpg
    <DESCRIPTION>CHART
    <TEXT>
    Document 9 - file: isba-20250320_g5.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>10
    <FILENAME>isba-20250320_g6.jpg
    <DESCRIPTION>PROXY CARD
    <TEXT>
    Document 10 - file: isba-20250320_g6.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>11
    <FILENAME>isba-20250320_g7.jpg
    <DESCRIPTION>PROXY CARD
    <TEXT>
    Document 11 - file: isba-20250320_g7.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>13
    <FILENAME>R1.htm
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 13 - file: R1.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>14
    <FILENAME>R2.htm
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 14 - file: R2.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>15
    <FILENAME>Show.js
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 15 - file: Show.js

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>16
    <FILENAME>report.css
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 16 - file: report.css

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>18
    <FILENAME>FilingSummary.xml
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 18 - file: FilingSummary.html

    Document 18 - RAW XML: FilingSummary.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>JSON
    <SEQUENCE>20
    <FILENAME>MetaLinks.json
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 20 - file: MetaLinks.json

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>ZIP
    <SEQUENCE>21
    <FILENAME>0000842517-25-000071-xbrl.zip
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 21 - file: 0000842517-25-000071-xbrl.zip

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>22
    <FILENAME>isba-20250320_htm.xml
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 22 - file: isba-20250320_htm.html

    Document 22 - RAW XML: isba-20250320_htm.xml

    </DOCUMENT>
    </SEC-DOCUMENT>