Allowance for Loan Losses - Troubled Debt Restructurings (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 SecurityLoan	Mar. 31, 2013 SecurityLoan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number	9	3
Pre-mod outstanding principal balance	$ 1,488	$ 257
Post-mod outstanding principal balance	1,456	260
Financial impact due to TDR taken as additional provision	64
Number that defaulted during the period	2
Recorded investment of TDRs that defaulted during the period	376
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions	(8)
RE Mortgage [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number	2
Pre-mod outstanding principal balance	695
Post-mod outstanding principal balance	695
Financial impact due to TDR taken as additional provision	37
Number that defaulted during the period
Recorded investment of TDRs that defaulted during the period
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions
RE Mortgage [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number	2
Pre-mod outstanding principal balance	256
Post-mod outstanding principal balance	259
Financial impact due to TDR taken as additional provision	9
Number that defaulted during the period	1
Recorded investment of TDRs that defaulted during the period	260
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions
Home equity lines of credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number	2	3
Pre-mod outstanding principal balance	279	257
Post-mod outstanding principal balance	279	260
Financial impact due to TDR taken as additional provision
Number that defaulted during the period
Recorded investment of TDRs that defaulted during the period
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions
Home equity loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number
Pre-mod outstanding principal balance
Post-mod outstanding principal balance
Financial impact due to TDR taken as additional provision
Number that defaulted during the period
Recorded investment of TDRs that defaulted during the period
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions
Auto Indirect [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number
Pre-mod outstanding principal balance
Post-mod outstanding principal balance
Financial impact due to TDR taken as additional provision
Number that defaulted during the period
Recorded investment of TDRs that defaulted during the period
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions
Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number
Pre-mod outstanding principal balance
Post-mod outstanding principal balance
Financial impact due to TDR taken as additional provision
Number that defaulted during the period
Recorded investment of TDRs that defaulted during the period
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions
C&I [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number	1
Pre-mod outstanding principal balance	38
Post-mod outstanding principal balance	38
Financial impact due to TDR taken as additional provision	18
Number that defaulted during the period	1
Recorded investment of TDRs that defaulted during the period	116
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions	(8)
Construction [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number	1
Pre-mod outstanding principal balance	102
Post-mod outstanding principal balance	85
Financial impact due to TDR taken as additional provision
Number that defaulted during the period
Recorded investment of TDRs that defaulted during the period
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions
Construction [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number	1
Pre-mod outstanding principal balance	118
Post-mod outstanding principal balance	100
Financial impact due to TDR taken as additional provision
Number that defaulted during the period
Recorded investment of TDRs that defaulted during the period
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions