Note 19 - Fair Value of Financial Instruments and Fair Value Measurements (Details Textual)	Dec. 31, 2016
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.

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