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v3.20.1

Allowance for Loan Losses (Details Textual) | Dec. 31, 2019 USD ($)
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Receivables [Abstract] |
Outstanding balance of high risk loans, minimum | $ 250,000

X
- Definition Minimum loan balance for reviewing. + References No definition available. + Details
Name: | cban_LoanBalanceForReviewingHighRiskLoansMinimum
Namespace Prefix: | cban_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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