Note 11 - Fair Value of Financial Instruments and Fair Value Measurements (Details Textual)	Jun. 30, 2018
Discounted Rate To Account For Selling And Marketing Costs	10.00%

Refers to the discounted rate to account for selling and marketing costs in fair value measurements.

No definition available.

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Namespace Prefix:	cban_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant