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v3.25.3

Allowance for Credit Losses - Narrative (Details) $ in Thousands | 9 Months Ended
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Sep. 30, 2025 USD ($)
Receivables [Abstract] |
Supportable forecast period (in years) | 1 year
Outstanding balance of high risk loans, minimum | $ 500

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- Definition Financing Receivable, Allowance for Credit Loss, Forecast Period + References No definition available. + Details
Name: | cban_FinancingReceivableAllowanceForCreditLossForecastPeriod
Namespace Prefix: | cban_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Loan Balance For Reviewing High Risk Loans Minimum + References No definition available. + Details
Name: | cban_LoanBalanceForReviewingHighRiskLoansMinimum
Namespace Prefix: | cban_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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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