XML 13 R1.htm IDEA: XBRL DOCUMENT v3.25.1
Cover Page - shares
 3 Months Ended
Mar. 31, 2025
May 07, 2025
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2025  
Document Transition Report false  
Entity File Number 0-18415  
Entity Registrant Name Isabella Bank Corp  
Entity Incorporation, State or Country Code MI  
Entity Tax Identification Number 38-2830092  
Entity Address, Address Line One 401 N. Main St  
Entity Address, City or Town Mt. Pleasant  
Entity Address, State or Province MI  
Entity Address, Postal Zip Code 48858  
City Area Code 989  
Local Phone Number 772-9471  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   7,382,358
Amendment Flag false  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q1  
Current Fiscal Year End Date --12-31  
Entity Central Index Key 0000842517