Financial Information of Colony Bankcorp, Inc. (Parent Only) - Balance Sheets, Parent Company - Share Info (Details) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Condensed Balance Sheet Statements, Captions [Line Items]
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	20,000,000	20,000,000
Common stock, shares issued (in shares)	9,498,783	9,498,783
Common stock, shares outstanding (in shares)	9,498,783	9,498,783
Parent Company
Condensed Balance Sheet Statements, Captions [Line Items]
Common stock, par value (in dollars per share)	$ 1.00	$ 1.00
Common stock, shares authorized (in shares)	20,000,000	20,000,000
Common stock, shares issued (in shares)	9,498,783	9,498,783