Note 11 - Fair Value of Financial Instruments and Fair Value Measurements (Details)	Sep. 30, 2015
Fair Value Disclosures [Abstract]
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