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Related Party Transactions - Narrative (Details) - USD ($) $ in Thousands | Dec. 31, 2025 | Dec. 31, 2024
--- | --- | ---
Principal Officers and Directors and Their Affiliates |  |
Related Party Transaction [Line Items] |  |
Total deposits | $ 5,050 | $ 4,024
Affiliated Entity | Isabella Bank Foundation |  |
Related Party Transaction [Line Items] |  |
Common stock, shares held by related party | 20,000 | 20,000

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