Consolidated Statements of Cash Flows (unaudited) (Parenthetical) $ in Millions	9 Months Ended
Sep. 30, 2022 USD ($)
Statement of Cash Flows [Abstract]
Transfer to held-to-maturity, unrealized loss	$ 34.0

Debt Securities, Available-for-Sale, Transfer To Held-to-maturity, Unrealized Gain (Loss)

No definition available.

Name:	cban_DebtSecuritiesAvailableForSaleTransferToHeldToMaturityUnrealizedGainLoss
Namespace Prefix:	cban_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration