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Related Party Transactions (Narrative) (Details) - USD ($) $ in Thousands | Dec. 31, 2024 | Dec. 31, 2023
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Principal Officers and Directors and Their Affiliates [Member] |  |
Related Party Transaction [Line Items] |  |
Total deposits | $ 4,024 | $ 7,735
Affiliated Entity [Member] | Isabella Bank Foundation [Member] |  |
Related Party Transaction [Line Items] |  |
Common Stock, Shares Held by Related Party | 20,000 | 20,000

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