Deposits (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Deposits [Abstract]
Aggregate amount of overdrawn deposit accounts reclassified as loan balances	$ 366cban_TotalAmountOfOverdrawnDeposit	$ 511cban_TotalAmountOfOverdrawnDeposit
Components of interest-bearing deposits [Abstract]
Interest-Bearing Demand	367,875us-gaap_DemandDepositAccounts	363,501us-gaap_DemandDepositAccounts
Savings	64,141us-gaap_DepositsSavingsDeposits	59,215us-gaap_DepositsSavingsDeposits
Time, $100,000 and Over	213,946us-gaap_TimeDeposits100000OrMore	210,503us-gaap_TimeDeposits100000OrMore
Other Time	211,310us-gaap_TimeDepositsLessThan100000	217,744us-gaap_TimeDepositsLessThan100000
Total Interest Bearing Deposits	857,272	850,963
Brokered deposits balances	26,236	26,298
Certificates of deposits, $100,000 or more	143,218cban_CertificatesOfDeposits100000OrMore	140,832cban_CertificatesOfDeposits100000OrMore
Scheduled maturities of certificates of deposits [Abstract]
One Year and Under	301,221us-gaap_TimeDepositMaturitiesYearOne	302,585us-gaap_TimeDepositMaturitiesYearOne
One to Three Years	92,919	98,219
Three Years and Over	31,116	27,443
Total	$ 425,256us-gaap_TimeDeposits	$ 428,247us-gaap_TimeDeposits

The aggregate amount of domestic and foreign certificates of deposit liabilities in denominations of $100,000 or more.

No definition available.

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Balance Type:	credit
Period Type:	instant

- Definition

Amount of certificates of deposits maturing between one and third fiscal year following the latest fiscal year. Time deposits include, but are not limited to, certificates of deposits, individual retirement accounts and open accounts.

+ References

No definition available.

+ Details

Name:	cban_CertificatesOfDepositsMaturitiesOneToThreeYears
Namespace Prefix:	cban_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of certificate of deposits maturing after the third fiscal year following the latest fiscal year.

+ References

No definition available.

+ Details

Name:	cban_CertificatesOfDepositsMaturitiesThreeYearsAndOver
Namespace Prefix:	cban_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Refers to the aggregate amount of overdrawn deposit accounts reclassified as loan balances as of balance sheet date.

+ References

No definition available.

+ Details

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

- Definition

The amount of money in accounts that may bear interest and that the depositor is entitled to withdraw at any time without prior notice.

+ References

+ Details

Name:	us-gaap_DemandDepositAccounts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DepositsAbstract
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- Details

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

- Definition

Amount of interest bearing deposits with no stated maturity, which may include passbook and statement savings accounts and money-market deposit accounts (MMDAs).

+ References

+ Details

Name:	us-gaap_DepositsSavingsDeposits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The aggregate of all domestic and foreign interest-bearing deposit liabilities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.12)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 12

-Article 9

+ Details

Name:	us-gaap_InterestBearingDepositLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of interest-bearing domestic third-party deposits placed by or through the assistance of a deposit broker, also known as brokered deposit liabilities.

+ References

+ Details

Name:	us-gaap_InterestBearingDomesticDepositBrokered
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of time deposits maturing in the next fiscal year following the latest fiscal year. Time deposits include, but are not limited to, certificates of deposits. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of deposits that cannot be withdrawn before a set date without penalty or for which notice of withdrawal is required. Time deposits include, but are not limited to, certificates of deposits, individual retirement accounts and open accounts.

+ References

+ Details

Name:	us-gaap_TimeDeposits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The aggregate amount of domestic and foreign time deposit liabilities (including certificates of deposits, individual retirement accounts and open accounts) in denominations of $100,000 or more.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 405

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6479006&loc=d3e64164-112818

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

-Publisher SEC

-Name Industry Guide

-Number 3

-Section V

-Paragraph A

-Subparagraph 4

+ Details

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Balance Type:	credit
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- Details

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Balance Type:	na
Period Type:	duration

- Definition

The aggregate amount of domestic or foreign time deposits (including certificates of deposits, individual retirement accounts and open accounts) that total to less than $100,000.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant