XML 101 R88.htm IDEA: XBRL DOCUMENT v3.25.0.1
Computation of Earnings Per Common Share (Schedule of Earnings Per Share) (Details) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Earnings Per Share [Abstract]      
Average number of common shares outstanding for basic calculation 7,465,343 7,511,591 7,549,878
Average number of common shares outstanding used to calculate diluted earnings per common share 7,482,374 7,575,492 7,647,612
Net Incomet $ 13,889 $ 18,167 $ 22,238
Basic (in dollars per share) $ 1.86 $ 2.42 $ 2.95
Diluted (in dollars per share) $ 1.86 $ 2.40 $ 2.91
Isabella Bank Corporation and Related Companies Deferred Compensation Plan for Directors      
Earnings Per Share [Abstract]      
Average potential effect of common shares in the Directors Plan [1] 0 34,962 70,329
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]      
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements [1] 0 34,962 70,329
Isabella Bank Corporation Restricted Stock Plan      
Earnings Per Share [Abstract]      
Average potential effect of common shares in the Directors Plan 17,031 28,939 27,405
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]      
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements 17,031 28,939 27,405
[1] Exclusive of shares held in the Rabbi Trust