Note 2 - Business Combination - Acquired Loans (Details) - Planters First Bank [Member]	Oct. 22, 2018 USD ($)
Contractually Required Payments Receivable	$ 20,749,515
Cash Flows Expected To Be Collected	20,749,515
Discounted FMV Adjustments	319,244
Carrying Value of Loans Receivable	$ 20,430,271

For receivables acquired in a business combination, excluding certain loans and debt securities acquired in a transfer (as defined), this element represents the best estimate at the acquisition date of the contractual cash flows expected to be collected, by major class of receivable, such as loans, direct finance leases (as defined), and any other class of receivables.

No definition available.

+ Details

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

- Definition

Fair value adjustment of acquired receivable from business combination, excluding certain loans and debt securities acquired in transfer.

+ References

No definition available.

+ Details

Name:	cban_BusinessCombinationAcquiredReceivablesDiscountedFairValueAdjustment
Namespace Prefix:	cban_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Fair value of acquired receivable from business combination, excluding certain loans and debt securities acquired in transfer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=84161108&loc=d3e4845-128472

+ Details

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

- Definition

For receivables acquired in a business combination, excluding certain loans and debt securities acquired in a transfer (as defined), this element represents the gross contractual amounts receivable, by major class of receivable, such as loans, direct finance leases (as defined), and any other class of receivables.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=84161108&loc=d3e4845-128472

+ Details

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

- Details

Name:	us-gaap_BusinessAcquisitionAxis=cban_PlantersFirstBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: