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, 2013 Contract	Sep. 30, 2012 Contract
Troubled Debt Restructurings [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	8	12
Pre-Modification Outstanding Recorded Investment	$ 3,740	$ 10,976
Post-Modification Outstanding Recorded Investment	3,502	9,933
Troubled Debt Restructurings [Member] | Commercial Non-Real Estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	1	1
Pre-Modification Outstanding Recorded Investment	926	790
Post-Modification Outstanding Recorded Investment	913	790
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	5	9
Pre-Modification Outstanding Recorded Investment	1,844	9,475
Post-Modification Outstanding Recorded Investment	1,746	8,582
Troubled Debt Restructurings [Member] | Residential Mortgage Loans [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	2	2
Pre-Modification Outstanding Recorded Investment	970	711
Post-Modification Outstanding Recorded Investment	843	561
Troubled Debt Restructurings [Member] | Consumer 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] | Originated loans [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	6	12
Pre-Modification Outstanding Recorded Investment	2,714	10,976
Post-Modification Outstanding Recorded Investment	2,526	9,933
Troubled Debt Restructurings [Member] | Originated loans [Member] | Commercial Non-Real Estate [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	1	1
Pre-Modification Outstanding Recorded Investment	926	790
Post-Modification Outstanding Recorded Investment	913	790
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	4	9
Pre-Modification Outstanding Recorded Investment	1,332	9,475
Post-Modification Outstanding Recorded Investment	1,270	8,582
Troubled Debt Restructurings [Member] | Originated loans [Member] | Residential Mortgage Loans [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts	1	2
Pre-Modification Outstanding Recorded Investment	456	711
Post-Modification Outstanding Recorded Investment	343	561
Troubled Debt Restructurings [Member] | Originated loans [Member] | Consumer 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] | 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	976
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	476
Troubled Debt Restructurings [Member] | 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	500
Troubled Debt Restructurings [Member] | Acquired loans [Member] | Consumer 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]
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 Mortgage 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] | Consumer 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 That Subsequently Defaulted [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts		2
Recorded Investment		1,787
Troubled Debt Restructurings That Subsequently Defaulted [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] | 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		2
Recorded Investment		1,787
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Residential Mortgage Loans [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Consumer loans [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		2
Recorded Investment		1,787
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
Recorded Investment
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		2
Recorded Investment		1,787
Troubled Debt Restructurings That Subsequently Defaulted [Member] | Originated loans [Member] | Residential Mortgage Loans [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 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]
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 Mortgage 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] | Consumer 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]
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 Mortgage 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] | Consumer loans [Member]
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Number of Contracts
Recorded Investment