Assets Acquired in FDIC-Assisted Acquisitions - Components of Covered Assets (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Covered loans	$ 529,792	$ 641,451	$ 778,746
Less: Credit risk adjustments	85,899	132,983	175,820
Less: Liquidity and rate adjustments	376	756	1,189
Total covered loans	443,517	507,712	601,737
OREO	75,960	105,347	104,177
Less: Fair value adjustments	13,782	17,074	20,710
Total covered OREO	62,178	88,273	83,467
Total covered assets	505,695	595,985	685,204
FDIC indemnification asset	105,513	159,724	203,801
American United Bank (AUB) [Member]
Covered loans	23,721	27,169	29,740
Less: Credit risk adjustments	2,114	2,481	2,542
Total covered loans	21,607	24,688	27,198
OREO	4,847	10,636	11,489
Less: Fair value adjustments		102
Total covered OREO	4,847	10,534	11,489
Total covered assets	26,454	35,222	38,687
FDIC indemnification asset	4,526	2,905	2,620
United Security Bank (USB) [Member]
Covered loans	23,298	27,286	40,355
Less: Credit risk adjustments	2,552	4,320	4,666
Total covered loans	20,746	22,966	35,689
OREO	4,127	7,087	7,192
Less: Fair value adjustments	140	99	50
Total covered OREO	3,987	6,988	7,142
Total covered assets	24,733	29,954	42,831
FDIC indemnification asset	5,802	6,619	6,757
Satilla Community Bank (SCB) [Member]
Covered loans	38,478	41,389	46,033
Less: Credit risk adjustments	2,882	3,285	840
Total covered loans	35,596	38,104	45,193
OREO	4,655	10,686	11,078
Less: Fair value adjustments	306	654	646
Total covered OREO	4,349	10,032	10,432
Total covered assets	39,945	48,136	55,625
FDIC indemnification asset	4,603	6,133	4,663
First Bank of Jacksonville (FBJ) [Member]
Covered loans	29,154	32,574	35,618
Less: Credit risk adjustments	5,086	6,204	6,645
Less: Liquidity and rate adjustments		27	59
Total covered loans	24,068	26,343	28,914
OREO	2,037	3,260	2,787
Less: Fair value adjustments	209	526	515
Total covered OREO	1,828	2,734	2,272
Total covered assets	25,896	29,077	31,186
FDIC indemnification asset	5,632	6,589	7,051
Darby Bank & Trust (DBT) [Member]
Covered loans	132,707	169,527	222,724
Less: Credit risk adjustments	27,386	41,631	60,218
Less: Liquidity and rate adjustments		207	455
Total covered loans	105,321	127,689	162,051
OREO	23,594	30,395	24,121
Less: Fair value adjustments	2,003	2,160	1,422
Total covered OREO	21,591	28,235	22,699
Total covered assets	126,912	155,924	184,750
FDIC indemnification asset	27,957	47,012	65,684
Tifton Banking Company (TBC) [Member]
Covered loans	37,560	46,796	63,593
Less: Credit risk adjustments	3,206	4,979	8,155
Less: Liquidity and rate adjustments	93	173	252
Total covered loans	34,261	41,644	55,186
OREO	7,069	11,089	8,616
Less: Fair value adjustments	1,650	1,381	1,184
Total covered OREO	5,419	9,708	7,432
Total covered assets	39,680	51,352	62,618
FDIC indemnification asset	6,083	8,073	14,838
High Trust Bank [HTB] [Member]
Covered loans	74,867	90,602	98,624
Less: Credit risk adjustments	9,702	16,072	20,676
Less: Liquidity and rate adjustments	45	52	60
Total covered loans	65,120	74,478	77,888
OREO	10,868	13,980	16,860
Less: Fair value adjustments	3,436	4,954	6,499
Total covered OREO	7,432	9,026	10,361
Total covered assets	72,552	83,504	88,249
FDIC indemnification asset	13,314	20,020	25,249
One Georgia Bank (OGB) [Member]
Covered loans	70,644	81,908	88,717
Less: Credit risk adjustments	11,450	17,127	22,041
Less: Liquidity and rate adjustments	118	136	156
Total covered loans	59,076	64,645	66,520
OREO	10,244	9,168	13,397
Less: Fair value adjustments	3,948	4,078	6,573
Total covered OREO	6,296	5,090	6,824
Total covered assets	65,372	69,735	73,344
FDIC indemnification asset	14,591	16,871	26,105
Central Bank of Georgia (CBG) [Member]
Covered loans	99,363	124,200	153,342
Less: Credit risk adjustments	21,521	36,884	50,037
Less: Liquidity and rate adjustments	120	161	207
Total covered loans	77,722	87,155	103,098
OREO	8,519	9,046	8,637
Less: Fair value adjustments	2,090	3,120	3,821
Total covered OREO	6,429	5,926	4,816
Total covered assets	84,151	93,081	107,914
FDIC indemnification asset	$ 23,005	$ 45,502	$ 50,834