Note 1 - Summary of Significant Accounting Policies (Details) - USD ($)	9 Months Ended
Sep. 30, 2015	Dec. 31, 2014
Note 1 - Summary of Significant Accounting Policies (Details) [Line Items]
Percentage of Loan Portfolio Concentrated in Loans Secured by Real Estate	86.00%
Discounted Percentage for Selling and Marketing Cost	10.00%
Probability of Uncertain Tax Positions of Being Realized Upon Settlement Minimum	50.00%
Other Assets [Member]
Note 1 - Summary of Significant Accounting Policies (Details) [Line Items]
Cash Surrender Value of Life Insurance (in Dollars)	$ 14,663	$ 14,531

Discounted percentage to account for selling and marketing costs.

No definition available.

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

- References

No definition available.

+ Details

Name:	cban_Note1SummaryofSignificantAccountingPoliciesDetailsLineItems
Namespace Prefix:	cban_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

Minimum probability of uncertain tax positions of being realized upon settlement.

+ References

No definition available.

+ Details

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

- Definition

Carrying amount as of the balance sheet date of amounts which could be received based on the terms of the insurance contract upon surrendering life policies owned by the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.17)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 4

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6812-107765

+ Details

Name:	us-gaap_CashSurrenderValueOfLifeInsurance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_OtherAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: