Allowance for Loan Losses - Analysis of Past Due and Nonaccrual Loans (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	$ 9,426	$ 10,136
60-89 Days	6,358	2,926
> 90 Days	9,933	23,126
Total past due	25,717	36,188
Current	1,433,118	1,361,147
Total Originated loans	1,458,835	1,397,335
> 90 Days and still accruing
Nonaccrual loans	53,261	61,769
PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	514	1,679
60-89 Days	1,921	63
> 90 Days	10	348
Total past due	2,445	2,090
Current	138,991	95,830
Total Originated loans	141,436	97,920
> 90 Days and still accruing
Nonaccrual loans	1,597	1,776
RE Mortgage [Member] | Residential [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	184	1,702
60-89 Days	1,023	278
> 90 Days	176	674
Total past due	1,383	2,654
Current	127,591	118,601
Total Originated loans	128,974	121,255
> 90 Days and still accruing
Nonaccrual loans	4,353	4,781
RE Mortgage [Member] | Residential [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days		1,024
60-89 Days
> 90 Days		43
Total past due		1,067
Current	61,808	4,346
Total Originated loans	61,808	5,413
> 90 Days and still accruing
Nonaccrual loans	265	113
RE Mortgage [Member] | Commercial [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	5,323	2,695
60-89 Days	2,887	1,578
> 90 Days	7,234	13,829
Total past due	15,444	18,102
Current	786,126	757,022
Total Originated loans	801,570	775,124
> 90 Days and still accruing
Nonaccrual loans	38,241	37,220
RE Mortgage [Member] | Commercial [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	514	500
60-89 Days	1,883
> 90 Days	10	148
Total past due	2,407	648
Current	59,697	71,442
Total Originated loans	62,104	72,090
> 90 Days and still accruing
Nonaccrual loans	800	1,218
Home equity lines of credit [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	3,258	3,371
60-89 Days	987	819
> 90 Days	2,007	3,395
Total past due	6,252	7,585
Current	315,260	304,086
Total Originated loans	321,512	311,671
> 90 Days and still accruing
Nonaccrual loans	6,098	8,486
Home equity lines of credit [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days		124
60-89 Days	38	63
> 90 Days		157
Total past due	38	344
Current	14,329	16,444
Total Originated loans	14,367	16,788
> 90 Days and still accruing
Nonaccrual loans	494	403
Home equity loans [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	67	67
60-89 Days	90	33
> 90 Days	254	217
Total past due	411	317
Current	12,434	12,694
Total Originated loans	12,845	13,011
> 90 Days and still accruing
Nonaccrual loans	490	465
Home equity loans [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days
60-89 Days
> 90 Days
Total past due
Current	281	342
Total Originated loans	281	342
> 90 Days and still accruing
Nonaccrual loans
Auto Indirect [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	38	77
60-89 Days		40
> 90 Days	40	79
Total past due	78	196
Current	1,273	3,620
Total Originated loans	1,351	3,816
> 90 Days and still accruing
Nonaccrual loans	59	174
Other Consumer [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	28	67
60-89 Days	2	40
> 90 Days	10	14
Total past due	40	121
Current	26,066	24,142
Total Originated loans	26,106	24,263
> 90 Days and still accruing
Nonaccrual loans	28	49
Other Consumer [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days		31
60-89 Days
> 90 Days
Total past due		31
Current	2,101	2,387
Total Originated loans	2,101	2,418
> 90 Days and still accruing
Nonaccrual loans	38	42
C&I [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	372	1,848
60-89 Days	939	138
> 90 Days	125	4,782
Total past due	1,436	6,768
Current	124,598	118,354
Total Originated loans	126,034	125,122
> 90 Days and still accruing
Nonaccrual loans	1,152	6,750
C&I [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days
60-89 Days
> 90 Days
Total past due
Current	775	869
Total Originated loans	775	869
> 90 Days and still accruing
Nonaccrual loans
Construction [Member] | Residential [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	107	309
60-89 Days	232
> 90 Days	19	42
Total past due	358	351
Current	26,011	11,526
Total Originated loans	26,369	11,877
> 90 Days and still accruing
Nonaccrual loans	2,588	3,312
Construction [Member] | Commercial [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	49
60-89 Days	198
> 90 Days	68	94
Total past due	315	94
Current	13,759	11,102
Total Originated loans	14,074	11,196
> 90 Days and still accruing
Nonaccrual loans	$ 252	$ 532