Loans and Allowance for Loan Losses (Details 4) (Acquired loans, USD $)	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Changes in the carrying value of acquired loans at the acquisition date
Balance at the beginning of the period	$ 370,581,000	$ 321,038,000
Fair value of acquired loans	234,245,000	222,434,000
Net reductions for payments, foreclosures, and accretion	(115,455,000)	(107,711,000)
Change in the allowance for loan losses on acquired loans	482,000	(29,870,000)
Balance at the end of the period	489,853,000	405,891,000
Changes in the carrying amount of accretable difference for acquired impaired and non-impaired loans
Balance at beginning of period	94,600,000	44,684,000
Interest income	(36,156,000)	(30,152,000)
Reclass of nonaccretable difference due to improvement in expected cash flows	26,399,000	42,273,000
Other changes, net	(12,418,000)	(5,947,000)
Balance at end of period	107,346,000	100,189,000
Threshold limit for provision of specific reserve on impaired loan	250,000
Threshold limit of loans for risk assessment by loan officers	500,000
Habersham Bank
Changes in the carrying amount of accretable difference for acquired impaired and non-impaired loans
Addition from acquisition		28,115,000
BankMeridian
Changes in the carrying amount of accretable difference for acquired impaired and non-impaired loans
Addition from acquisition		21,216,000
Peoples
Changes in the carrying amount of accretable difference for acquired impaired and non-impaired loans
Addition from acquisition	34,921,000
Loans Impaired at Acquisition
Changes in the carrying value of acquired loans at the acquisition date
Balance at the beginning of the period	146,955,000	143,059,000
Fair value of acquired loans	30,735,000	92,541,000
Net reductions for payments, foreclosures, and accretion	(48,774,000)	(46,606,000)
Change in the allowance for loan losses on acquired loans	(953,000)	(25,438,000)
Balance at the end of the period	127,963,000	163,556,000
Loans Not Impaired at Acquisition
Changes in the carrying value of acquired loans at the acquisition date
Balance at the beginning of the period	223,626,000	177,979,000
Fair value of acquired loans	203,510,000	129,893,000
Net reductions for payments, foreclosures, and accretion	(66,681,000)	(61,105,000)
Change in the allowance for loan losses on acquired loans	1,435,000	(4,432,000)
Balance at the end of the period	$ 361,890,000	$ 242,335,000