Allowance for Loan Losses - Narrative (Details)	Sep. 30, 2021 USD ($)
Receivables [Abstract]
Outstanding balance of high risk loans, minimum	$ 250,000

Loan Balance For Reviewing High Risk Loans Minimum

No definition available.

Name:	cban_LoanBalanceForReviewingHighRiskLoansMinimum
Namespace Prefix:	cban_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant