Assets Acquired In FDIC-Assisted Acquisitions - Loans Receivable at Acquisition Date for Loans with Deterioration in Credit Quality (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Contractually required principal payments receivable	$ 137,407	$ 241,786	$ 356,508	$ 109,810
Non-accretable difference	53,603	95,076	106,763	47,708
Present value of cash flows expected to be collected	83,804	146,710	249,745	62,102
Accretable difference	10,390	22,574	35,245	3,550
Fair value of loans acquired with deterioration credit quality	73,414	124,136	214,500	58,552
American United Bank (AUB) [Member]
Contractually required principal payments receivable				65,438
Non-accretable difference				26,416
Present value of cash flows expected to be collected				39,022
Accretable difference				1,945
Fair value of loans acquired with deterioration credit quality				37,077
United Security Bank (USB) [Member]
Contractually required principal payments receivable				44,372
Non-accretable difference				21,292
Present value of cash flows expected to be collected				23,080
Accretable difference				1,605
Fair value of loans acquired with deterioration credit quality				21,475
Satilla Community Bank (SCB) [Member]
Contractually required principal payments receivable			49,864
Non-accretable difference			22,885
Present value of cash flows expected to be collected			26,979
Accretable difference			1,508
Fair value of loans acquired with deterioration credit quality			25,471
First Bank of Jacksonville (FBJ) [Member]
Contractually required principal payments receivable			29,474
Non-accretable difference			6,672
Present value of cash flows expected to be collected			22,802
Accretable difference			3,564
Fair value of loans acquired with deterioration credit quality			19,238
Tifton Banking Company (TBC) [Member]
Contractually required principal payments receivable			51,908
Non-accretable difference			20,569
Present value of cash flows expected to be collected			31,339
Accretable difference			1,366
Fair value of loans acquired with deterioration credit quality			29,973
Darby Bank & Trust (DBT) [Member]
Contractually required principal payments receivable			225,262
Non-accretable difference			56,637
Present value of cash flows expected to be collected			168,625
Accretable difference			28,807
Fair value of loans acquired with deterioration credit quality			139,818
High Trust Bank [HTB] [Member]
Contractually required principal payments receivable		136,928
Non-accretable difference		49,447
Present value of cash flows expected to be collected		87,481
Accretable difference		13,265
Fair value of loans acquired with deterioration credit quality		74,216
One Georgia Bank (OGB) [Member]
Contractually required principal payments receivable		104,858
Non-accretable difference		45,629
Present value of cash flows expected to be collected		59,229
Accretable difference		9,309
Fair value of loans acquired with deterioration credit quality		49,920
Central Bank of Georgia (CBG) [Member]
Contractually required principal payments receivable	137,407
Non-accretable difference	53,603
Present value of cash flows expected to be collected	83,804
Accretable difference	10,390
Fair value of loans acquired with deterioration credit quality	$ 73,414