Assets Acquired In FDIC-Assisted Acquisitions - Components of Covered Assets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Covered loans	$ 641,451	$ 739,190
Less Credit risk adjustments	132,983	166,107
Less Liquidity and rate adjustments	756	1,594
Total covered loans	507,712	571,489
OREO	105,347	101,685
Less Fair value adjustments	17,074	23,068
Total covered OREO	88,273	78,617
Total covered assets	595,985	650,106
FDIC indemnification asset	159,724	242,394
American United Bank (AUB) [Member]
Covered loans	27,169	34,242
Less Credit risk adjustments	2,481	3,236
Total covered loans	24,688	31,006
OREO	10,636	11,100
Less Fair value adjustments	102
Total covered OREO	10,534	11,100
Total covered assets	35,222	42,106
FDIC indemnification asset	2,905	7,271
United Security Bank (USB) [Member]
Covered loans	27,286	51,409
Less Credit risk adjustments	4,320	5,259
Less Liquidity and rate adjustments		50
Total covered loans	22,966	46,100
OREO	7,087	7,445
Less Fair value adjustments	99	50
Total covered OREO	6,988	7,395
Total covered assets	29,954	53,495
FDIC indemnification asset	6,619	10,648
Satilla Community Bank (SCB) [Member]
Covered loans	41,389	56,780
Less Credit risk adjustments	3,285	5,779
Less Liquidity and rate adjustments		155
Total covered loans	38,104	50,846
OREO	10,686	10,635
Less Fair value adjustments	654	500
Total covered OREO	10,032	10,135
Total covered assets	48,136	60,981
FDIC indemnification asset	6,133	6,527
First Bank of Jacksonville (FBJ) [Member]
Covered loans	32,574	40,106
Less Credit risk adjustments	6,204	7,473
Less Liquidity and rate adjustments	27	92
Total covered loans	26,343	32,541
OREO	3,260	2,370
Less Fair value adjustments	526	641
Total covered OREO	2,734	1,729
Total covered assets	29,077	34,270
FDIC indemnification asset	6,589	8,551
Darby Bank & Trust (DBT) [Member]
Covered loans	169,527	260,883
Less Credit risk adjustments	41,631	68,757
Less Liquidity and rate adjustments	207	703
Total covered loans	127,689	191,423
OREO	30,395	28,947
Less Fair value adjustments	2,160	2,763
Total covered OREO	28,235	26,184
Total covered assets	155,924	217,607
FDIC indemnification asset	47,012	105,528
Tifton Banking Company (TBC) [Member]
Covered loans	46,796	79,586
Less Credit risk adjustments	4,979	14,358
Less Liquidity and rate adjustments	173	331
Total covered loans	41,644	64,897
OREO	11,089	8,441
Less Fair value adjustments	1,381	1,274
Total covered OREO	9,708	7,167
Total covered assets	51,352	72,064
FDIC indemnification asset	8,073	18,628
High Trust Bank [HTB] [Member]
Covered loans	90,602	110,899
Less Credit risk adjustments	16,072	28,024
Less Liquidity and rate adjustments	52	73
Total covered loans	74,478	82,802
OREO	13,980	20,132
Less Fair value adjustments	4,954	10,171
Total covered OREO	9,026	9,961
Total covered assets	83,504	92,763
FDIC indemnification asset	20,020	48,289
One Georgia Bank (OGB) [Member]
Covered loans	81,908	105,285
Less Credit risk adjustments	17,127	33,221
Less Liquidity and rate adjustments	136	190
Total covered loans	64,645	71,874
OREO	9,168	12,615
Less Fair value adjustments	4,078	7,669
Total covered OREO	5,090	4,946
Total covered assets	69,735	76,820
FDIC indemnification asset	16,871	36,952
Central Bank of Georgia (CBG) [Member]
Covered loans	124,200
Less Credit risk adjustments	36,884
Less Liquidity and rate adjustments	161
Total covered loans	87,155
OREO	9,046
Less Fair value adjustments	3,120
Total covered OREO	5,926
Total covered assets	93,081
FDIC indemnification asset	$ 45,502