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Loans and Allowance for Credit Losses - Schedule of Information Regarding Credit Exposure (Parenthetical) (Details) - USD ($) | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023
Receivables [Abstract] |  |
Financing receivable originated checking accounts writeoffs | $ 607,000 | $ 480,000

X
- Definition Financing receivable originated checking accounts writeoffs. + References No definition available. + Details
Name: | cofs_FinancingReceivableOriginatedCheckingAccountsWriteoffs
Namespace Prefix: | cofs_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_ReceivablesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration