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Fair Value of Financial Instruments and Fair Value Measurements (Details Textual) - USD ($) | 3 Months Ended | 6 Months Ended
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Mar. 31, 2020 | Jun. 30, 2019
Fair Value Disclosures [Abstract] |  |
Fair value input, discount amount | 10.00% |
Transfers out of level 3 | $ 0 | $ 2,009,000

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- Definition Refers to the discounted rate to account for selling and marketing costs in fair value measurements. + References No definition available. + Details
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Namespace Prefix: | cban_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- References No definition available. + Details
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- Definition Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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