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Employee Benefit Plan (Details) (USD $) | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Employee Benefit Plan [Abstract] |  |  |
Employee service period | 6 years |  |
Discretionary contributions by employer | $ 401,497 us-gaap_DefinedBenefitPlanContributionsByEmployer | $ 0 us-gaap_DefinedBenefitPlanContributionsByEmployer | $ 0 us-gaap_DefinedBenefitPlanContributionsByEmployer

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- Definition Represents minimum service period for employees to be fully vested in company contributions. + References No definition available. + Details
Name: | cban_EmployeeServicePeriod
Namespace Prefix: | cban_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_CompensationAndRetirementDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition The increase in the fair value of plan assets from contributions made by the employer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanContributionsByEmployer
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration