Allowance for Loan Losses - Troubled Debt Restructurings (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014 SecurityLoan	Jun. 30, 2013 SecurityLoan	Jun. 30, 2014 SecurityLoan	Jun. 30, 2013 SecurityLoan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number	7	14	16	17
Pre-mod outstanding principal balance	$ 946	$ 5,419	$ 2,433	$ 5,677
Post-mod outstanding principal balance	962	5,427	2,417	5,687
Financial impact due to TDR taken as additional provision	12	424	76	424
Number that defaulted during the period	2	10	4	10
Recorded investment of TDRs that defaulted during the period	315	2,482	691	2,482
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions		2		2
RE Mortgage [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number	1	2	3	2
Pre-mod outstanding principal balance	112	432	806	432
Post-mod outstanding principal balance	112	436	806	436
Financial impact due to TDR taken as additional provision		151	37	151
Number that defaulted during the period	1	2	1	2
Recorded investment of TDRs that defaulted during the period	152	181	152	181
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions		(3)		(3)
RE Mortgage [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number	2	6	4	6
Pre-mod outstanding principal balance	568	4,555	824	4,555
Post-mod outstanding principal balance	571	4,555	830	4,555
Financial impact due to TDR taken as additional provision	8	22	18	22
Number that defaulted during the period	1	4	2	4
Recorded investment of TDRs that defaulted during the period	163	931	423	931
Home equity lines of credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number	1	4	3	7
Pre-mod outstanding principal balance	200	324	479	582
Post-mod outstanding principal balance	212	328	491	588
Financial impact due to TDR taken as additional provision		193		193
Home equity loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number	1		1
Pre-mod outstanding principal balance	32		32
Post-mod outstanding principal balance	33		33
C&I [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number	2	2	3	2
Pre-mod outstanding principal balance	34	108	72	108
Post-mod outstanding principal balance	34	108	72	108
Financial impact due to TDR taken as additional provision	4	58	21	58
Number that defaulted during the period		3	1	3
Recorded investment of TDRs that defaulted during the period		1,297	116	1,297
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
Number that defaulted during the period		1		1
Recorded investment of TDRs that defaulted during the period		73		73
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions		5		5
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