Regulatory Capital Matters - Narrative (Details)	Jan. 01, 2019	Jan. 01, 2016
Banking And Thrift Disclosure [Abstract]
Percentage of risk-weighted assets		0.625%
Increase in percentage of risk-weighted assets		0.625%
Final level of percentage of risk-weighted assets	2.50%

The yearly increase in minimum Tier One Capital Ratio (Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action as per Basel III framework.

No definition available.

Name:	cban_IncreaseInTierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Namespace Prefix:	cban_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant