Assets Acquired In FDIC-Assisted Acquisitions - Components of Covered Assets (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Covered loans	$ 575,966	$ 641,451	$ 860,391
Less Credit risk adjustments	114,699	132,983	205,531
Less Liquidity and rate adjustments	543	756	1,483
Total covered loans	460,724	507,712	653,377
OREO	91,677	105,347	112,783
Less Fair value adjustments	13,762	17,074	26,980
Total covered OREO	77,915	88,273	85,803
Total covered assets	538,639	595,985	739,180
FDIC indemnification asset	160,979	159,724	220,016
American United Bank (AUB) [Member]
Covered loans	25,001	27,169	33,063
Less Credit risk adjustments	2,508	2,481	2,672
Total covered loans	22,493	24,688	30,391
OREO	8,079	10,636	11,842
Less Fair value adjustments	100	102
Total covered OREO	7,979	10,534	11,842
Total covered assets	30,472	35,222	42,233
FDIC indemnification asset	4,176	2,905	2,648
United Security Bank (USB) [Member]
Covered loans	25,921	27,286	48,017
Less Credit risk adjustments	3,879	4,320	5,083
Total covered loans	22,042	22,966	42,934
OREO	5,379	7,087	8,401
Less Fair value adjustments	139	99	50
Total covered OREO	5,240	6,988	8,351
Total covered assets	27,282	29,954	51,285
FDIC indemnification asset	9,932	6,619	6,621
Satilla Community Bank (SCB) [Member]
Covered loans	40,008	41,389	53,643
Less Credit risk adjustments	3,189	3,285	5,628
Less Liquidity and rate adjustments			52
Total covered loans	36,819	38,104	47,963
OREO	6,670	10,686	10,833
Less Fair value adjustments	299	654	405
Total covered OREO	6,371	10,032	10,428
Total covered assets	43,190	48,136	58,391
FDIC indemnification asset	8,189	6,133	7,660
First Bank of Jacksonville (FBJ) [Member]
Covered loans	31,479	32,574	38,116
Less Credit risk adjustments	5,662	6,204	6,994
Less Liquidity and rate adjustments	11	27	76
Total covered loans	25,806	26,343	31,046
OREO	1,450	3,260	2,674
Less Fair value adjustments	93	526	534
Total covered OREO	1,357	2,734	2,140
Total covered assets	27,163	29,077	33,186
FDIC indemnification asset	6,840	6,589	7,540
Darby Bank & Trust (DBT) [Member]
Covered loans	146,178	169,527	245,117
Less Credit risk adjustments	35,461	41,631	64,530
Less Liquidity and rate adjustments	83	207	579
Total covered loans	110,634	127,689	180,008
OREO	25,990	30,395	28,759
Less Fair value adjustments	1,895	2,160	2,253
Total covered OREO	24,095	28,235	26,506
Total covered assets	134,729	155,924	206,514
FDIC indemnification asset	37,333	47,012	65,932
Tifton Banking Company (TBC) [Member]
Covered loans	42,302	46,796	74,893
Less Credit risk adjustments	4,450	4,979	14,052
Less Liquidity and rate adjustments	133	173	292
Total covered loans	37,719	41,644	60,549
OREO	10,478	11,089	6,678
Less Fair value adjustments	1,814	1,381	880
Total covered OREO	8,664	9,708	5,798
Total covered assets	46,383	51,352	66,347
FDIC indemnification asset	8,050	8,073	18,166
High Trust Bank [HTB] [Member]
Covered loans	82,202	90,602	106,730
Less Credit risk adjustments	14,068	16,072	23,637
Less Liquidity and rate adjustments	49	52	73
Total covered loans	68,085	74,478	83,020
OREO	14,823	13,980	17,755
Less Fair value adjustments	3,445	4,954	8,055
Total covered OREO	11,378	9,026	9,700
Total covered assets	79,463	83,504	92,720
FDIC indemnification asset	21,423	20,020	29,997
One Georgia Bank (OGB) [Member]
Covered loans	73,279	81,908	96,271
Less Credit risk adjustments	14,877	17,127	27,105
Less Liquidity and rate adjustments	127	136	190
Total covered loans	58,275	64,645	68,976
OREO	10,384	9,168	12,049
Less Fair value adjustments	4,144	4,078	7,037
Total covered OREO	6,240	5,090	5,012
Total covered assets	64,515	69,735	73,988
FDIC indemnification asset	18,687	16,871	30,126
Central Bank of Georgia (CBG) [Member]
Covered loans	109,596	124,200	164,541
Less Credit risk adjustments	30,605	36,884	55,830
Less Liquidity and rate adjustments	140	161	221
Total covered loans	78,851	87,155	108,490
OREO	8,424	9,046	13,792
Less Fair value adjustments	1,833	3,120	7,766
Total covered OREO	6,591	5,926	6,026
Total covered assets	85,442	93,081	114,516
FDIC indemnification asset	$ 46,349	$ 45,502	$ 51,326