Assets Acquired in FDIC-Assisted Acquisitions - Components of Covered Assets (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Covered loans	$ 482,259	$ 641,451	$ 699,229
Less: Credit risk adjustments	64,307	132,983	151,999
Less: Liquidity and rate adjustments	303	756	996
Total covered loans	417,649	507,712	546,234
OREO	64,184	105,347	106,979
Less: Fair value adjustments	11,632	17,074	18,084
Total covered OREO	52,552	88,273	88,895
Total covered assets	470,201	595,985	635,129
FDIC indemnification asset	81,763	159,724	198,440
American United Bank (AUB) [Member]
Covered loans	19,336	27,169	28,955
Less: Credit risk adjustments	915	2,481	2,532
Total covered loans	18,421	24,688	26,423
OREO	3,338	10,636	10,342
Less: Fair value adjustments	3	102
Total covered OREO	3,335	10,534	10,342
Total covered assets	21,756	35,222	36,765
FDIC indemnification asset	3,704	2,905	3,256
United Security Bank (USB) [Member]
Covered loans	21,168	27,286	33,145
Less: Credit risk adjustments	1,665	4,320	5,036
Total covered loans	19,503	22,966	28,109
OREO	3,066	7,087	7,641
Less: Fair value adjustments	139	99	99
Total covered OREO	2,927	6,988	7,542
Total covered assets	22,430	29,954	35,651
FDIC indemnification asset	2,796	6,619	8,408
Satilla Community Bank (SCB) [Member]
Covered loans	35,555	41,389	44,340
Less: Credit risk adjustments	1,902	3,285	3,892
Total covered loans	33,653	38,104	40,448
OREO	5,348	10,686	10,464
Less: Fair value adjustments	429	654	646
Total covered OREO	4,919	10,032	9,818
Total covered assets	38,572	48,136	50,266
FDIC indemnification asset	4,020	6,133	6,130
First Bank of Jacksonville (FBJ) [Member]
Covered loans	27,222	32,574	33,312
Less: Credit risk adjustments	3,965	6,204	6,299
Less: Liquidity and rate adjustments		27	43
Total covered loans	23,257	26,343	26,970
OREO	1,582	3,260	3,407
Less: Fair value adjustments	170	526	572
Total covered OREO	1,412	2,734	2,835
Total covered assets	24,669	29,077	29,805
FDIC indemnification asset	4,990	6,589	6,731
Darby Bank & Trust (DBT) [Member]
Covered loans	116,685	169,527	186,815
Less: Credit risk adjustments	21,739	41,631	47,598
Less: Liquidity and rate adjustments		207	331
Total covered loans	94,946	127,689	138,886
OREO	19,720	30,395	33,404
Less: Fair value adjustments	1,639	2,160	2,798
Total covered OREO	18,081	28,235	30,606
Total covered assets	113,027	155,924	169,492
FDIC indemnification asset	23,955	47,012	63,789
Tifton Banking Company (TBC) [Member]
Covered loans	35,588	46,796	51,084
Less: Credit risk adjustments	2,519	4,979	5,790
Less: Liquidity and rate adjustments	54	173	212
Total covered loans	33,015	41,644	45,082
OREO	5,912	11,089	10,110
Less: Fair value adjustments	843	1,381	1,533
Total covered OREO	5,069	9,708	8,577
Total covered assets	38,084	51,352	53,659
FDIC indemnification asset	4,315	8,073	15,559
High Trust Bank (HTB) [Member]
Covered loans	70,156	90,602	95,904
Less: Credit risk adjustments	8,232	16,072	18,727
Less: Liquidity and rate adjustments	41	52	56
Total covered loans	61,883	74,478	77,121
OREO	6,998	13,980	15,219
Less: Fair value adjustments	2,445	4,954	5,766
Total covered OREO	4,553	9,026	9,453
Total covered assets	66,436	83,504	86,574
FDIC indemnification asset	11,065	20,020	23,698
One Georgia Bank (OGB) [Member]
Covered loans	63,794	81,908	86,091
Less: Credit risk adjustments	6,658	17,127	18,719
Less: Liquidity and rate adjustments	108	136	146
Total covered loans	57,028	64,645	67,226
OREO	9,921	9,168	7,874
Less: Fair value adjustments	3,918	4,078	3,663
Total covered OREO	6,003	5,090	4,211
Total covered assets	63,031	69,735	71,437
FDIC indemnification asset	9,458	16,871	21,419
Central Bank of Georgia (CBG) [Member]
Covered loans	92,755	124,200	139,583
Less: Credit risk adjustments	16,712	36,884	43,406
Less: Liquidity and rate adjustments	100	161	208
Total covered loans	75,943	87,155	95,969
OREO	8,299	9,046	8,518
Less: Fair value adjustments	2,046	3,120	3,007
Total covered OREO	6,253	5,926	5,511
Total covered assets	82,196	93,081	101,480
FDIC indemnification asset	$ 17,460	$ 45,502	$ 49,450