Loans and Allowance for Loan Losses - Schedule of Troubled Debt Restructurings Occurred During Period by Portfolio Segment (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014 Contract	Sep. 30, 2013 Contract
Troubled Debt Restructurings [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	6	10
Pre-Modification Outstanding Recorded Investment	$ 3,925	$ 4,767
Post-Modification Outstanding Recorded Investment	3,233	4,557
Troubled Debt Restructurings [Member] | Commercial Non-Real Estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts		1
Pre-Modification Outstanding Recorded Investment		925
Post-Modification Outstanding Recorded Investment		920
Troubled Debt Restructurings [Member] | Construction and Land Development [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Pre-Modification Outstanding Recorded Investment
Post-Modification Outstanding Recorded Investment
Troubled Debt Restructurings [Member] | Commercial Real Estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	2	6
Pre-Modification Outstanding Recorded Investment	2,430	2,356
Post-Modification Outstanding Recorded Investment	2,385	2,290
Troubled Debt Restructurings [Member] | Residential Mortgages [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	4	3
Pre-Modification Outstanding Recorded Investment	1,495	1,486
Post-Modification Outstanding Recorded Investment	848	1,347
Troubled Debt Restructurings [Member] | Consumer [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Pre-Modification Outstanding Recorded Investment
Post-Modification Outstanding Recorded Investment
Troubled Debt Restructurings [Member] | Originated Loans [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	6	8
Pre-Modification Outstanding Recorded Investment	3,925	3,740
Post-Modification Outstanding Recorded Investment	3,233	3,563
Troubled Debt Restructurings [Member] | 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		925
Post-Modification Outstanding Recorded Investment		920
Troubled Debt Restructurings [Member] | Originated Loans [Member] | Construction and Land Development [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Pre-Modification Outstanding Recorded Investment
Post-Modification Outstanding Recorded Investment
Troubled Debt Restructurings [Member] | Originated Loans [Member] | Commercial Real Estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	2	5
Pre-Modification Outstanding Recorded Investment	2,430	1,844
Post-Modification Outstanding Recorded Investment	2,385	1,789
Troubled Debt Restructurings [Member] | Originated Loans [Member] | Residential Mortgages [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	4	2
Pre-Modification Outstanding Recorded Investment	1,495	971
Post-Modification Outstanding Recorded Investment	848	854
Troubled Debt Restructurings [Member] | Originated Loans [Member] | Consumer [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Pre-Modification Outstanding Recorded Investment
Post-Modification Outstanding Recorded Investment
Troubled Debt Restructurings [Member] | Acquired Loans [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts		2
Pre-Modification Outstanding Recorded Investment		1,027
Post-Modification Outstanding Recorded Investment		994
Troubled Debt Restructurings [Member] | Acquired Loans [Member] | Commercial Non-Real Estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Pre-Modification Outstanding Recorded Investment
Post-Modification Outstanding Recorded Investment
Troubled Debt Restructurings [Member] | Acquired Loans [Member] | Construction and Land Development [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Pre-Modification Outstanding Recorded Investment
Post-Modification Outstanding Recorded Investment
Troubled Debt Restructurings [Member] | 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		501
Troubled Debt Restructurings [Member] | Acquired Loans [Member] | Residential Mortgages [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts		1
Pre-Modification Outstanding Recorded Investment		515
Post-Modification Outstanding Recorded Investment		493
Troubled Debt Restructurings [Member] | Acquired Loans [Member] | Consumer [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Pre-Modification Outstanding Recorded Investment
Post-Modification Outstanding Recorded Investment
Troubled Debt Restructurings [Member] | Covered Loans [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Pre-Modification Outstanding Recorded Investment
Post-Modification Outstanding Recorded Investment
Troubled Debt Restructurings [Member] | Covered Loans [Member] | Commercial Non-Real Estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Pre-Modification Outstanding Recorded Investment
Post-Modification Outstanding Recorded Investment
Troubled Debt Restructurings [Member] | Covered Loans [Member] | Construction and Land Development [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Pre-Modification Outstanding Recorded Investment
Post-Modification Outstanding Recorded Investment
Troubled Debt Restructurings [Member] | Covered Loans [Member] | Commercial Real Estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Pre-Modification Outstanding Recorded Investment
Post-Modification Outstanding Recorded Investment
Troubled Debt Restructurings [Member] | Covered Loans [Member] | Residential Mortgages [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Pre-Modification Outstanding Recorded Investment
Post-Modification Outstanding Recorded Investment
Troubled Debt Restructurings [Member] | Covered Loans [Member] | Consumer [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Pre-Modification Outstanding Recorded Investment
Post-Modification Outstanding Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	1
Recorded Investment	909
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Commercial Non-Real Estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	1
Recorded Investment	909
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Construction and Land Development [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Commercial Real Estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Residential Mortgages [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Consumer [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Originated Loans [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	1
Recorded Investment	909
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Originated Loans [Member] | Commercial Non-Real Estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	1
Recorded Investment	909
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Originated Loans [Member] | Construction and Land Development [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Originated Loans [Member] | Commercial Real Estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Originated Loans [Member] | Residential Mortgages [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Originated Loans [Member] | Consumer [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Acquired Loans [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Acquired Loans [Member] | Commercial Non-Real Estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Acquired Loans [Member] | Construction and Land Development [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Acquired Loans [Member] | Commercial Real Estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Acquired Loans [Member] | Residential Mortgages [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Acquired Loans [Member] | Consumer [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Covered Loans [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Covered Loans [Member] | Commercial Non-Real Estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Covered Loans [Member] | Construction and Land Development [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Covered Loans [Member] | Commercial Real Estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Covered Loans [Member] | Residential Mortgages [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Covered Loans [Member] | Consumer [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment