Summary of Significant Accounting Policies (Details)	3 Months Ended
Mar. 31, 2021
Accounting Policies [Abstract]
Percentage of Loan Portfolio Concentrated in Loans Secured by Real Estate	78.00%

Percentage of loan portfolio concentrated in loans secured by real estate.

No definition available.

Name:	cban_PercentageOfLoanPortfolioConcentratedInLoansSecuredByRealEstate
Namespace Prefix:	cban_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration