Note 12 - Regulatory Capital Matters (Details)	Sep. 30, 2015
Disclosure Text Block [Abstract]
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets Rule 1	0.625%
Increase in Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	0.625%
Tier 1 Capital Conservation Buffer of Risk Weighted Assets	2.50%

The 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.

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Namespace Prefix:	cban_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant