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Allowance for Credit Losses - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2023 | Sep. 30, 2023
Receivables [Abstract] |  |
Supportable forecast period | 1 year |
Outstanding balance of high risk loans, minimum |  | $ 0.5

X
- 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