Minimum loan balance for reviewing.

No definition available.

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

- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953676-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=121585226&loc=d3e18845-111554

+ Details

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

- Definition

Number of financing receivable contracts modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953682-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of interest income on financing receivable on nonaccrual status.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919258-210447

+ Details

Name:	us-gaap_FinancingReceivableNonaccrualInterestIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_LoansAndLeasesReceivableDisclosureLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121593590&loc=d3e4428-111522

+ Details

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

- Definition

Amount of unfunded portion of contractual agreement to lend funds to borrower for financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121585226&loc=d3e18794-111554

+ Details

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

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditLossStatusAxis=us-gaap_FinancialAssetOriginatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=cban_OtherCommercialLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=cban_LoanModificationsCARESActMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Loans - (Details Textual)	3 Months Ended		9 Months Ended
Loans - (Details Textual)	Sep. 30, 2020 USD ($) loan	Sep. 30, 2019 USD ($) loan	Sep. 30, 2020 USD ($) loan	Sep. 30, 2019 USD ($) loan	Dec. 31, 2019 USD ($)
Loans and Leases Receivable Disclosure [Line Items]
Loan originations	$ 1,101,606,000		$ 1,101,606,000		$ 968,814,000
Outstanding balance of high risk loans, minimum	250,000		250,000
Interest income on impaired loans	104,000	$ 274,000	154,000	$ 477,000
Unfunded commitments to lend	$ 0		$ 0
Loan contracts restructured	3		3
Number of loans that subsequently defaulted \| loan	0	0	0	0
Loans	$ 1,101,606,000		$ 1,101,606,000		968,814,000
Commercial Real Estate Portfolio Segment
Loans and Leases Receivable Disclosure [Line Items]
Loan originations	638,283,000		$ 638,283,000		636,336,000
Loan contracts restructured			2
Troubled debt restructuring	131,000		$ 131,000
Loans	638,283,000		638,283,000		636,336,000
Legacy Loans
Loans and Leases Receivable Disclosure [Line Items]
Loan originations	1,005,172,000		1,005,172,000		847,100,000
Loans	1,005,172,000		1,005,172,000		847,100,000
Legacy Loans \| Commercial Real Estate Portfolio Segment
Loans and Leases Receivable Disclosure [Line Items]
Loan originations	574,262,000		574,262,000		564,979,000
Loans	574,262,000		574,262,000		564,979,000
Other commercial real estate
Loans and Leases Receivable Disclosure [Line Items]
Loan originations	509,992,000		509,992,000		540,239,000
Loans	509,992,000		509,992,000		540,239,000
Other commercial real estate \| Commercial Real Estate Portfolio Segment
Loans and Leases Receivable Disclosure [Line Items]
Loan originations	509,992,000		509,992,000		540,239,000
Loans	509,992,000		509,992,000		540,239,000
Other commercial real estate \| Legacy Loans \| Commercial Real Estate Portfolio Segment
Loans and Leases Receivable Disclosure [Line Items]
Loan originations	464,100,000		464,100,000		481,943,000
Loans	464,100,000		$ 464,100,000		$ 481,943,000
Commercial Loan
Loans and Leases Receivable Disclosure [Line Items]
Loan contracts restructured			1
Troubled debt restructuring	97,000		$ 97,000
Loan Modifications, CARES Act
Loans and Leases Receivable Disclosure [Line Items]
Loan originations	12,600,000		12,600,000
Loans	$ 12,600,000		$ 12,600,000