Allowance for Loan Losses - Analysis of Past Due and Nonaccrual Loans (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due: 30-59 Days	$ 3,436	$ 8,321
60-89 Days	1,475	1,661
> 90 Days	2,960	4,824
Total past due	7,871	14,806
Current	1,561,181	1,468,740
Total orig. loans	1,569,052	1,483,546
> 90 Days and still accruing	360
Nonaccrual loans	33,489	45,131
PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due: 30-59 Days	192	1,673
60-89 Days	1,208	390
> 90 Days	36	217
Total past due	1,436	2,280
Current	147,594	132,469
Total orig. loans	149,030	134,749
Nonaccrual loans	1,113	1,866
RE Mortgage [Member] | Residential [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due: 30-59 Days	112	2,272
60-89 Days	509	284
> 90 Days	591	447
Total past due	1,212	3,003
Current	140,642	126,879
Total orig. loans	141,854	129,882
Nonaccrual loans	4,018	4,697
RE Mortgage [Member] | Residential [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due: 30-59 Days	192	799
60-89 Days	1,208
Total past due	1,400	799
Current	81,366	59,676
Total orig. loans	82,766	60,475
Nonaccrual loans	349	262
RE Mortgage [Member] | Commercial [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due: 30-59 Days	933	2,304
60-89 Days	205
> 90 Days	1,490	2,213
Total past due	2,628	4,517
Current	904,349	820,395
Total orig. loans	906,977	824,912
> 90 Days and still accruing	360
Nonaccrual loans	21,471	30,732
RE Mortgage [Member] | Commercial [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due: 30-59 Days		512
60-89 Days		352
> 90 Days		217
Total past due		1,081
Current	52,070	56,597
Total orig. loans	52,070	57,678
Nonaccrual loans	419	1,139
Home equity lines of credit [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due: 30-59 Days	1,692	3,121
60-89 Days	514	1,070
> 90 Days	521	1,050
Total past due	2,727	5,241
Current	298,268	310,966
Total orig. loans	300,995	316,207
Nonaccrual loans	4,257	4,972
Home equity lines of credit [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due: 30-59 Days		313
60-89 Days		38
> 90 Days	36
Total past due	36	351
Current	11,708	13,225
Total orig. loans	11,744	13,576
Nonaccrual loans	314	429
Home equity loans [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due: 30-59 Days	202	264
60-89 Days	208	16
> 90 Days	127	312
Total past due	537	592
Current	21,072	13,257
Total orig. loans	21,609	13,849
Nonaccrual loans	838	719
Home equity loans [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	153	253
Total orig. loans	153	253
Auto Indirect [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due: 30-59 Days	2	24
60-89 Days	1	1
> 90 Days	20	33
Total past due	23	58
Current	189	888
Total orig. loans	212	946
Nonaccrual loans	23	54
Other Consumer [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due: 30-59 Days	81	40
60-89 Days	11	16
> 90 Days	10	7
Total past due	102	63
Current	27,099	25,545
Total orig. loans	27,201	25,608
Nonaccrual loans	19	26
Other Consumer [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due: 30-59 Days		49
Total past due		49
Current	1,823	2,025
Total orig. loans	1,823	2,074
Nonaccrual loans	31	36
C&I [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due: 30-59 Days	414	296
60-89 Days	27	76
> 90 Days	99	749
Total past due	540	1,121
Current	128,251	123,529
Total orig. loans	128,791	124,650
Nonaccrual loans	312	1,280
C&I [Member] | PNCI loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	474	693
Total orig. loans	474	693
Construction [Member] | Residential [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
> 90 Days		13
Total past due		13
Current	22,860	30,354
Total orig. loans	22,860	30,367
Nonaccrual loans	2,437	2,473
Construction [Member] | Commercial [Member] | Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
60-89 Days		198
> 90 Days	102
Total past due	102	198
Current	18,451	16,927
Total orig. loans	18,553	17,125
Nonaccrual loans	$ 114	$ 178