Loans and Allowance for Loan Losses - Schedule of Troubled Debt Restructurings Occurred During Period by Portfolio Segment (Detail) (Troubled Debt Restructurings [Member], USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013 Contract	Jun. 30, 2012 Contract
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	8	4
Pre-Modification Outstanding Recorded Investment	$ 3,639	$ 3,909
Post-Modification Outstanding Recorded Investment	3,609	3,850
Commercial non-real estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	1
Pre-Modification Outstanding Recorded Investment	926
Post-Modification Outstanding Recorded Investment	921
Construction and Land development [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts		1
Pre-Modification Outstanding Recorded Investment		1,593
Post-Modification Outstanding Recorded Investment		1,556
Commercial real estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	5	2
Pre-Modification Outstanding Recorded Investment	1,844	1,644
Post-Modification Outstanding Recorded Investment	1,820	1,626
Residential mortgage loans [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	2	1
Pre-Modification Outstanding Recorded Investment	869	672
Post-Modification Outstanding Recorded Investment	868	668
Originated loans [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	6	4
Pre-Modification Outstanding Recorded Investment	2,613	3,909
Post-Modification Outstanding Recorded Investment	2,584	3,850
Originated loans [Member] | Commercial non-real estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	1
Pre-Modification Outstanding Recorded Investment	926
Post-Modification Outstanding Recorded Investment	921
Originated loans [Member] | Construction and Land development [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts		1
Pre-Modification Outstanding Recorded Investment		1,593
Post-Modification Outstanding Recorded Investment		1,556
Originated loans [Member] | Commercial real estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	4	2
Pre-Modification Outstanding Recorded Investment	1,332	1,644
Post-Modification Outstanding Recorded Investment	1,309	1,626
Originated loans [Member] | Residential mortgage loans [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	1	1
Pre-Modification Outstanding Recorded Investment	355	672
Post-Modification Outstanding Recorded Investment	354	668
Acquired loans [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	2
Pre-Modification Outstanding Recorded Investment	1,026
Post-Modification Outstanding Recorded Investment	1,025
Acquired loans [Member] | Commercial real estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	1
Pre-Modification Outstanding Recorded Investment	512
Post-Modification Outstanding Recorded Investment	511
Acquired loans [Member] | Residential mortgage loans [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	1
Pre-Modification Outstanding Recorded Investment	514
Post-Modification Outstanding Recorded Investment	$ 514