Subordinated Deferrable Interest Debentures - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Preferred Stock [Line Items]
Rate per annum of principal amount	3.11%
Principal amount issued	$ 27,662,000	$ 50,727,000
Scenario, Forecast [Member]
Preferred Stock [Line Items]
Principal amount outstanding	5,000,000
Aggregate principal amount	5,155,000
Ameris Statutory Trust I [Member]
Preferred Stock [Line Items]
Aggregate principal amount	37,114,000
Principal amount issued	36,000,000
LIBOR Rate	1.63%
Rate per annum of principal amount	1.94%
Trust preferred securities mature	Dec. 15, 2036
First National Banc Statutory Trust One [Member]
Preferred Stock [Line Items]
Principal amount of trust preferred securities	$ 5,000,000
LIBOR rate	2.80%
Maturity period of trust preferred securities	30 years