Assets Acquired in FDIC-Assisted Acquisitions - Schedule of Acquisition Details (Detail)	3 Months Ended
	Mar. 31, 2015 Entity
American United Bank (AUB) [Member]
Business Acquisition [Line Items]
Bank Acquired	American United Bank ("AUB")
Branches	1
Date Acquired	Oct. 23, 2009
United Security Bank (USB) [Member]
Business Acquisition [Line Items]
Bank Acquired	United Security Bank ("USB")
Branches	2
Date Acquired	Nov. 06, 2009
Satilla Community Bank (SCB) [Member]
Business Acquisition [Line Items]
Bank Acquired	Satilla Community Bank ("SCB")
Branches	1
Date Acquired	May 14, 2010
First Bank of Jacksonville (FBJ) [Member]
Business Acquisition [Line Items]
Bank Acquired	First Bank of Jacksonville ("FBJ")
Branches	2
Date Acquired	Oct. 22, 2010
Tifton Banking Company (TBC) [Member]
Business Acquisition [Line Items]
Bank Acquired	Tifton Banking Company ("TBC")
Branches	1
Date Acquired	Nov. 12, 2010
Darby Bank & Trust (DBT) [Member]
Business Acquisition [Line Items]
Bank Acquired	Darby Bank & Trust ("DBT")
Branches	7
Date Acquired	Nov. 12, 2010
High Trust Bank (HTB) [Member]
Business Acquisition [Line Items]
Bank Acquired	High Trust Bank ("HTB")
Branches	2
Date Acquired	Jul. 15, 2011
One Georgia Bank (OGB) [Member]
Business Acquisition [Line Items]
Bank Acquired	One Georgia Bank ("OGB")
Branches	1
Date Acquired	Jul. 15, 2011
Central Bank of Georgia (CBG) [Member]
Business Acquisition [Line Items]
Bank Acquired	Central Bank of Georgia Bank ("CBG")
Branches	5
Date Acquired	Feb. 24, 2012
Montgomery Bank & Trust (MBT) [Member]
Business Acquisition [Line Items]
Bank Acquired	Montgomery Bank & Trust ("MBT")
Branches	2
Date Acquired	Jul. 06, 2012