Assets Acquired In FDIC-Assisted Acquisitions - Estimated Fair Value of Assets And Liabilities Assumed (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
American United Bank (AUB) [Member]
Schedule of Business Acquisitions by Acquisition Purchase Price Allocation [Line Items]
Cash	$ 26,452
Investment securities	10,242
Loans	56,482
Foreclosed property	2,165
FDIC loss share asset	24,200
Core deposit intangible	187
Other assets	1,266
Total assets	120,994
Deposits	100,470
FHLB advances	7,802
Other liabilities	277
Total liabilities	108,549
Net assets acquired	12,445
United Security Bank (USB) [Member]
Schedule of Business Acquisitions by Acquisition Purchase Price Allocation [Line Items]
Cash	41,490
Investment securities	8,335
Federal funds sold	2,605
Loans	83,646
Foreclosed property	8,069
FDIC loss share asset	21,640
Core deposit intangible	386
Other assets	3,001
Total assets	169,172
Deposits	141,094
FHLB advances	1,504
Other liabilities	453
Total liabilities	143,051
Net assets acquired	26,121
Satilla Community Bank (SCB) [Member]
Schedule of Business Acquisitions by Acquisition Purchase Price Allocation [Line Items]
Cash	(33,093)
Investment securities	10,814
Federal funds sold	12,661
Loans	68,751
Foreclosed property	2,012
FDIC loss share asset	22,400
Core deposit intangible	185
Other assets	612
Total assets	84,342
Deposits	75,530
Other liabilities	604
Total liabilities	76,134
Net assets acquired	8,208
First Bank of Jacksonville (FBJ) [Member]
Schedule of Business Acquisitions by Acquisition Purchase Price Allocation [Line Items]
Cash	10,669
Investment securities	7,343
Federal funds sold	5,690
Loans	40,454
Foreclosed property	1,816
FDIC loss share asset	11,307
Core deposit intangible	132
Other assets	298
Total assets	77,709
Deposits	71,869
FHLB advances	2,613
Other liabilities	842
Total liabilities	75,324
Net assets acquired	2,385
Tifton Banking Company (TBC) [Member]
Schedule of Business Acquisitions by Acquisition Purchase Price Allocation [Line Items]
Cash	4,862
Investment securities	7,060
Loans	92,568
Foreclosed property	3,472
FDIC loss share asset	22,807
Core deposit intangible	175
Other assets	1,092
Total assets	132,036
Deposits	132,939
Other liabilities	53
Total liabilities	132,992
Net assets acquired	(956)
Darby Bank & Trust (DBT) [Member]
Schedule of Business Acquisitions by Acquisition Purchase Price Allocation [Line Items]
Cash	(58,158)
Investment securities	105,562
Loans	261,340
Foreclosed property	22,026
FDIC loss share asset	112,404
Core deposit intangible	1,180
Other assets	3,957
Total assets	448,311
Deposits	386,958
FHLB advances	2,724
Other liabilities	54,418
Total liabilities	444,100
Net assets acquired	4,211
High Trust Bank (HTB) [Member]
Schedule of Business Acquisitions by Acquisition Purchase Price Allocation [Line Items]
Cash	36,432
Investment securities	14,770
Loans	84,732
Foreclosed property	10,272
FDIC loss share asset	49,485
Other assets	1,772
Total assets	197,463
Deposits	175,887
Other liabilities	2,654
Total liabilities	178,541
Net assets acquired	18,922
One Georgia Bank (OGB) [Member]
Schedule of Business Acquisitions by Acquisition Purchase Price Allocation [Line Items]
Cash	1,585
Investment securities	28,891
Federal funds sold	5,070
Loans	74,843
Foreclosed property	7,242
FDIC loss share asset	45,488
Other assets	2,933
Total assets	166,052
Deposits	136,101
FHLB advances	21,107
Other liabilities	899
Total liabilities	158,107
Net assets acquired	7,945
Central Bank of Georgia (CBG) [Member]
Schedule of Business Acquisitions by Acquisition Purchase Price Allocation [Line Items]
Cash	65,050
Investment securities	39,920
Loans	124,782
Foreclosed property	6,177
FDIC loss share asset	52,654
Core deposit intangible	1,149
Other assets	3,457
Total assets	293,189
Deposits	261,036
FHLB advances	10,334
Other liabilities	1,782
Total liabilities	273,152
Net assets acquired	20,037
Montgomery Bank & Trust (MBT) [Member]
Schedule of Business Acquisitions by Acquisition Purchase Price Allocation [Line Items]
Cash	155,466
Loans	1,218
Other assets	183
Total assets	156,867
Deposits	156,699
Other liabilities	168
Total liabilities	$ 156,867