Assets Acquired in FDIC-Assisted Acquisitions - Components of Covered Assets (Detail) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Covered Assets [Line Items]
Covered loans	$ 345,172,000	$ 482,259,000	$ 443,322,000
Less: Fair value adjustments	31,583,000	64,610,000	53,085,000
Total covered loans	313,589,000	417,649,000	390,237,000
OREO	33,315,000	64,184,000	55,827,000
Less: Fair value adjustments	4,432,000	11,632,000	9,934,000
Total covered OREO	28,883,000	52,552,000	45,893,000
Total covered assets	342,472,000	470,201,000	436,130,000
FDIC loss-share receivable	38,233,000	81,763,000	65,441,000
American United Bank (AUB) [Member]
Covered Assets [Line Items]
Covered loans	8,902,000	19,336,000	15,787,000
Less: Fair value adjustments		915,000	231,000
Total covered loans	8,902	18,421,000	15,556,000
OREO	666,000	3,338,000	4,264,000
Less: Fair value adjustments		3,000
Total covered OREO	666,000	3,335,000	4,264,000
Total covered assets	9,568,000	21,756,000	19,820,000
FDIC loss-share receivable	882,000	3,704,000	1,452,000
United Security Bank (USB) [Member]
Covered Assets [Line Items]
Covered loans	13,576,000	21,168,000	18,504,000
Less: Fair value adjustments	351,000	1,665,000	1,427,000
Total covered loans	13,225,000	19,503,000	17,077,000
OREO	2,134,000	3,066,000	2,865,000
Less: Fair value adjustments	48,000	139,000	141,000
Total covered OREO	2,086,000	2,927,000	2,724,000
Total covered assets	15,311,000	22,430,000	19,801,000
FDIC loss-share receivable	(439,000)	2,796,000	889,000
Satilla Community Bank (SCB) [Member]
Covered Assets [Line Items]
Covered loans	28,534,000	35,555,000	34,637,000
Less: Fair value adjustments	789,000	1,902,000	1,483,000
Total covered loans	27,745,000	33,653,000	33,154,000
OREO	2,665,000	5,348,000	3,461,000
Less: Fair value adjustments	308,000	429,000	303,000
Total covered OREO	2,357,000	4,919,000	3,158,000
Total covered assets	30,102,000	38,572,000	36,312,000
FDIC loss-share receivable	1,855,000	4,020,000	3,175,000
First Bank of Jacksonville (FBJ) [Member]
Covered Assets [Line Items]
Covered loans	22,421,000	27,222,000	25,891,000
Less: Fair value adjustments	2,346,000	3,965,000	3,730,000
Total covered loans	20,075,000	23,257,000	22,161,000
OREO	1,578,000	1,582,000	1,880,000
Less: Fair value adjustments	90,000	170,000	242,000
Total covered OREO	1,488,000	1,412,000	1,638,000
Total covered assets	21,563,000	24,669,000	23,799,000
FDIC loss-share receivable	2,138,000	4,990,000	3,689,000
Darby Bank & Trust (DBT) [Member]
Covered Assets [Line Items]
Covered loans	75,683,000	116,685,000	105,157,000
Less: Fair value adjustments	8,531,000	21,739,000	17,819,000
Total covered loans	67,152,000	94,946,000	87,338,000
OREO	9,804,000	19,720,000	17,023,000
Less: Fair value adjustments	1,024,000	1,639,000	1,282,000
Total covered OREO	8,780,000	18,081,000	15,741,000
Total covered assets	75,932,000	113,027,000	103,079,000
FDIC loss-share receivable	9,337,000	23,955,000	18,724,000
Tifton Banking Company (TBC) [Member]
Covered Assets [Line Items]
Covered loans	25,577,000	35,588,000	32,590,000
Less: Fair value adjustments	1,465,000	2,573,000	2,354,000
Total covered loans	24,112,000	33,015,000	30,236,000
OREO	3,552,000	5,912,000	4,844,000
Less: Fair value adjustments	394,000	843,000	745,000
Total covered OREO	3,158,000	5,069,000	4,099,000
Total covered assets	27,270,000	38,084,000	34,335,000
FDIC loss-share receivable	2,542,000	4,315,000	3,721,000
High Trust Bank (HTB) [Member]
Covered Assets [Line Items]
Covered loans	54,317,000	70,156,000	67,126,000
Less: Fair value adjustments	5,761,000	8,273,000	7,359,000
Total covered loans	48,556,000	61,883,000	59,767,000
OREO	3,477,000	6,998,000	6,374,000
Less: Fair value adjustments	1,239,000	2,445,000	2,304,000
Total covered OREO	2,238,000	4,553,000	4,070,000
Total covered assets	50,794,000	66,436,000	63,837,000
FDIC loss-share receivable	7,152,000	11,065,000	9,325,000
One Georgia Bank (OGB) [Member]
Covered Assets [Line Items]
Covered loans	48,889,000	63,794,000	58,512,000
Less: Fair value adjustments	4,160,000	6,766,000	5,067,000
Total covered loans	44,729,000	57,028,000	53,445,000
OREO	2,244,000	9,921,000	7,506,000
Less: Fair value adjustments	39,000	3,918,000	2,984,000
Total covered OREO	2,205,000	6,003,000	4,522,000
Total covered assets	46,934,000	63,031,000	57,967,000
FDIC loss-share receivable	5,803,000	9,458,000	9,645,000
Central Bank of Georgia (CBG) [Member]
Covered Assets [Line Items]
Covered loans	67,273,000	92,755,000	85,118,000
Less: Fair value adjustments	8,180,000	16,812,000	13,615,000
Total covered loans	59,093,000	75,943,000	71,503,000
OREO	7,195,000	8,299,000	7,610,000
Less: Fair value adjustments	1,290,000	2,046,000	1,933,000
Total covered OREO	5,905,000	6,253,000	5,677,000
Total covered assets	64,998,000	82,196,000	77,180,000
FDIC loss-share receivable	$ 8,963,000	$ 17,460,000	$ 14,821,000