Loans - Summary of Loans Modified (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 Contract	Mar. 31, 2012 Contract
Troubled Debt Restructured Loan Modifications by Class [Line Items]
Pre- modification outstanding recorded investment	$ 60	$ 5,872
Post- modification outstanding recorded investment	60	5,867
Number of loans	1	7
Other Loans Held for Sale [Member]
Troubled Debt Restructured Loan Modifications by Class [Line Items]
Pre- modification outstanding recorded investment
Post- modification outstanding recorded investment
Number of loans
Rate Concessions [Member]
Troubled Debt Restructured Loan Modifications by Class [Line Items]
Pre- modification outstanding recorded investment	60
Post- modification outstanding recorded investment	60
Number of loans	1
Term concession [Member]
Troubled Debt Restructured Loan Modifications by Class [Line Items]
Pre- modification outstanding recorded investment		4,089
Post- modification outstanding recorded investment		4,089
Number of loans		1
Rate and term Concessions [Member]
Troubled Debt Restructured Loan Modifications by Class [Line Items]
Pre- modification outstanding recorded investment		1,783
Post- modification outstanding recorded investment		1,778
Number of loans		6
Construction, land development, and other land loans [Member]
Troubled Debt Restructured Loan Modifications by Class [Line Items]
Pre- modification outstanding recorded investment	60	4,089
Post- modification outstanding recorded investment	60	4,089
Number of loans	1	1
Nonfarm nonresidential [Member]
Troubled Debt Restructured Loan Modifications by Class [Line Items]
Pre- modification outstanding recorded investment		1,568
Post- modification outstanding recorded investment		1,568
Number of loans		5
Commercial real estate [Member]
Troubled Debt Restructured Loan Modifications by Class [Line Items]
Pre- modification outstanding recorded investment	60	5,657
Post- modification outstanding recorded investment	60	5,657
Number of loans	1	6
Commercial and Industrial [Member]
Troubled Debt Restructured Loan Modifications by Class [Line Items]
Pre- modification outstanding recorded investment		215
Post- modification outstanding recorded investment		210
Number of loans		1
Loans, Gross [Member]
Troubled Debt Restructured Loan Modifications by Class [Line Items]
Pre- modification outstanding recorded investment	60	5,872
Post- modification outstanding recorded investment	$ 60	$ 5,867
Number of loans	1	7