Fair Value of Financial Instruments and Fair Value Measurements - Narrative (Details)	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair value input, discounted amount	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