Allowance for Loan Losses - Presentation of Credit Quality Indicators (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	$ 1,765,871	$ 1,672,007	$ 1,657,051
Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	1,569,052	1,483,546
PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	149,030	134,749
PCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	47,789	53,712
Pass [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	1,490,458	1,394,438
Pass [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	139,778	123,715
Special mention [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	20,905	24,411
Special mention [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	5,243	6,336
Substandard [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	57,689	64,684
Substandard [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	4,009	4,698
Loss [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		13
RE Mortgage [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	228,407	195,013	197,129
RE Mortgage [Member] | Residential [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	141,854	129,882
RE Mortgage [Member] | Residential [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	82,766	60,475
RE Mortgage [Member] | Residential [Member] | PCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	3,787	4,656
RE Mortgage [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	985,746	912,850	894,346
RE Mortgage [Member] | Commercial [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	906,977	824,912
RE Mortgage [Member] | Commercial [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	52,070	57,678
RE Mortgage [Member] | Commercial [Member] | PCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	26,699	30,260
RE Mortgage [Member] | Pass [Member] | Residential [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	133,922	121,969
RE Mortgage [Member] | Pass [Member] | Residential [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	82,180	59,798
RE Mortgage [Member] | Pass [Member] | Commercial [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	857,171	768,596
RE Mortgage [Member] | Pass [Member] | Commercial [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	44,652	48,548
RE Mortgage [Member] | Special mention [Member] | Residential [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	832	1,265
RE Mortgage [Member] | Special mention [Member] | Commercial [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	13,626	15,862
RE Mortgage [Member] | Special mention [Member] | Commercial [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	4,697	5,810
RE Mortgage [Member] | Substandard [Member] | Residential [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	7,100	6,648
RE Mortgage [Member] | Substandard [Member] | Residential [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	586	677
RE Mortgage [Member] | Substandard [Member] | Commercial [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	36,180	40,454
RE Mortgage [Member] | Substandard [Member] | Commercial [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	2,721	3,320
RE Mortgage [Member] | Loss [Member] | Residential [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans
RE Mortgage [Member] | Loss [Member] | Commercial [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans
Home equity lines of credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	321,942	339,866	346,348
Home equity lines of credit [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	300,995	316,207
Home equity lines of credit [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	11,744	13,576
Home equity lines of credit [Member] | PCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	9,203	10,083
Home equity lines of credit [Member] | Pass [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	288,680	302,232
Home equity lines of credit [Member] | Pass [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	10,879	12,716
Home equity lines of credit [Member] | Special mention [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	3,290	4,529
Home equity lines of credit [Member] | Special mention [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	229	195
Home equity lines of credit [Member] | Substandard [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	9,025	9,446
Home equity lines of credit [Member] | Substandard [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	636	665
Home equity lines of credit [Member] | Loss [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans
Home equity loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	22,378	14,588	13,730
Home equity loans [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	21,609	13,849
Home equity loans [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	153	253
Home equity loans [Member] | PCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	616	486
Home equity loans [Member] | Pass [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	19,402	12,284
Home equity loans [Member] | Pass [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	153	253
Home equity loans [Member] | Special mention [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	767	504
Home equity loans [Member] | Substandard [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	1,440	1,061
Home equity loans [Member] | Loss [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans
Auto Indirect [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	212	946	1,351
Auto Indirect [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	212	946
Auto Indirect [Member] | Pass [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	145	717
Auto Indirect [Member] | Special mention [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	20	118
Auto Indirect [Member] | Substandard [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	47	111
Auto Indirect [Member] | Loss [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans
Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	29,088	27,763	28,282
Other Consumer [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	27,201	25,608
Other Consumer [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	1,823	2,074
Other Consumer [Member] | PCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	64	81
Other Consumer [Member] | Pass [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	26,639	24,653
Other Consumer [Member] | Pass [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	1,719	2,020
Other Consumer [Member] | Special mention [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	347	756
Other Consumer [Member] | Special mention [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	38	18
Other Consumer [Member] | Substandard [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	215	196
Other Consumer [Member] | Substandard [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	66	36
Other Consumer [Member] | Loss [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		3
C&I [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	135,085	131,878	133,616
C&I [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	128,791	124,650
C&I [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	474	693
C&I [Member] | PCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	5,820	6,535
C&I [Member] | Pass [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	126,554	121,580
C&I [Member] | Pass [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	195	380
C&I [Member] | Special mention [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	1,131	938
C&I [Member] | Special mention [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	279	313
C&I [Member] | Substandard [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	1,106	2,122
C&I [Member] | Loss [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		10
Construction [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	24,386	31,933	27,601
Construction [Member] | Residential [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	22,860	30,367
Construction [Member] | Residential [Member] | PCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	1,526	1,566
Construction [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	18,627	17,170	14,648
Construction [Member] | Commercial [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	18,553	17,125
Construction [Member] | Commercial [Member] | PCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	74	45
Construction [Member] | Pass [Member] | Residential [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	19,565	25,836
Construction [Member] | Pass [Member] | Commercial [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	18,380	16,571
Construction [Member] | Special mention [Member] | Residential [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	858	96
Construction [Member] | Special mention [Member] | Commercial [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	34	343
Construction [Member] | Substandard [Member] | Residential [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	2,437	4,435
Construction [Member] | Substandard [Member] | Commercial [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	139	211
Construction [Member] | Loss [Member] | Residential [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans
Construction [Member] | Loss [Member] | Commercial [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans