Allowance for Loan Losses - Analysis of Past Due and Nonaccrual Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	$ 7,512	$ 10,172
Current	2,168,097	1,978,573
Total orig. loans	2,175,609	1,988,745
> 90 Days and still accruing	0	0
Nonaccrual loans	10,022	22,824
PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	1,281	8,924
Current	446,396	485,064
Total orig. loans	447,677	493,988
> 90 Days and still accruing	0	0
Nonaccrual loans	3,789	5,398
Home Equity Lines of Credit [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	1,795	1,877
Current	272,054	283,542
Total orig. loans	273,849	285,419
> 90 Days and still accruing	0	0
Nonaccrual loans	2,826	3,379
Home Equity Lines of Credit [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	59	367
Current	26,520	28,968
Total orig. loans	26,579	29,335
> 90 Days and still accruing	0	0
Nonaccrual loans	512	676
Other Consumer [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	65	71
Current	29,558	28,927
Total orig. loans	29,623	28,998
> 90 Days and still accruing	0	0
Nonaccrual loans	9	21
Other Consumer [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	29	23
Current	2,719	3,344
Total orig. loans	2,748	3,367
> 90 Days and still accruing	0	0
Nonaccrual loans	8	33
C&I [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	1,321	2,221
Current	188,173	168,099
Total orig. loans	189,494	170,320
> 90 Days and still accruing	0	0
Nonaccrual loans	444	976
C&I [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		1
Current	16,062	19,743
Total orig. loans	16,062	19,744
> 90 Days and still accruing	0	0
30-59 Days [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	4,647	4,635
30-59 Days [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	89	7,259
30-59 Days [Member] | Home Equity Lines of Credit [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	1,326	1,033
30-59 Days [Member] | Home Equity Lines of Credit [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	48	92
30-59 Days [Member] | Other Consumer [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	47	12
30-59 Days [Member] | Other Consumer [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	21
30-59 Days [Member] | C&I [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	611	2,197
30-59 Days [Member] | C&I [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		1
60-89 Days [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	1,152	1,196
60-89 Days [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	817	13
60-89 Days [Member] | Home Equity Lines of Credit [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	250	324
60-89 Days [Member] | Home Equity Lines of Credit [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	11
60-89 Days [Member] | Other Consumer [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	9	40
60-89 Days [Member] | Other Consumer [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		13
60-89 Days [Member] | C&I [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	415
> 90 Days [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	1,713	4,341
> 90 Days [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	375	1,652
> 90 Days [Member] | Home Equity Lines of Credit [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	219	520
> 90 Days [Member] | Home Equity Lines of Credit [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		275
> 90 Days [Member] | Other Consumer [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	9	19
> 90 Days [Member] | Other Consumer [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	8	10
> 90 Days [Member] | C&I [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	295	24
Home Equity Loans [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	864	825
Current	35,653	33,892
Total orig. loans	36,517	34,717
> 90 Days and still accruing	0	0
Nonaccrual loans	1,396	1,195
Home Equity Loans [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	53	94
Current	3,801	3,924
Total orig. loans	3,854	4,018
> 90 Days and still accruing	0	0
Nonaccrual loans	70	109
Home Equity Loans [Member] | 30-59 Days [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	272	402
Home Equity Loans [Member] | 30-59 Days [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	20	23
Home Equity Loans [Member] | 60-89 Days [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	110	341
Home Equity Loans [Member] | 60-89 Days [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	33
Home Equity Loans [Member] | > 90 Days [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	482	82
Home Equity Loans [Member] | > 90 Days [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		71
Auto Indirect [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
> 90 Days and still accruing	0	0
Auto Indirect [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
> 90 Days and still accruing	0	0
Construction [Member] | Residential [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	48,608	31,778
Total orig. loans	48,608	31,778
> 90 Days and still accruing	0	0
Nonaccrual loans	11	12
Construction [Member] | Residential [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	13,174	13,636
Total orig. loans	13,174	13,636
> 90 Days and still accruing	0	0
Construction [Member] | Commercial [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	397
Current	77,803	66,285
Total orig. loans	78,200	66,285
> 90 Days and still accruing	0	0
Construction [Member] | Commercial [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		490
Current	9,121	7,999
Total orig. loans	9,121	8,489
> 90 Days and still accruing	0	0
Nonaccrual loans		490
Construction [Member] | 30-59 Days [Member] | Commercial [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	397
Construction [Member] | > 90 Days [Member] | Commercial [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		490
RE Mortgage [Member] | Residential [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	460	1,062
Current	221,000	206,523
Total orig. loans	221,460	207,585
> 90 Days and still accruing	0	0
Nonaccrual loans	2,375	3,045
RE Mortgage [Member] | Residential [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	316	3,164
Current	94,805	101,371
Total orig. loans	95,121	104,535
> 90 Days and still accruing	0	0
Nonaccrual loans	532	348
RE Mortgage [Member] | Commercial [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	2,610	4,116
Current	1,295,248	1,159,527
Total orig. loans	1,297,858	1,163,643
> 90 Days and still accruing	0	0
Nonaccrual loans	2,961	14,196
RE Mortgage [Member] | Commercial [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	824	4,785
Current	280,194	306,079
Total orig. loans	281,018	310,864
> 90 Days and still accruing	0	0
Nonaccrual loans	2,667	3,742
RE Mortgage [Member] | 30-59 Days [Member] | Residential [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	46	791
RE Mortgage [Member] | 30-59 Days [Member] | Residential [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		3,106
RE Mortgage [Member] | 30-59 Days [Member] | Commercial [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	1,948	200
RE Mortgage [Member] | 30-59 Days [Member] | Commercial [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due		4,037
RE Mortgage [Member] | 60-89 Days [Member] | Residential [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	70
RE Mortgage [Member] | 60-89 Days [Member] | Residential [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	29
RE Mortgage [Member] | 60-89 Days [Member] | Commercial [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	298	491
RE Mortgage [Member] | 60-89 Days [Member] | Commercial [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	744
RE Mortgage [Member] | > 90 Days [Member] | Residential [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	344	271
RE Mortgage [Member] | > 90 Days [Member] | Residential [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	287	58
RE Mortgage [Member] | > 90 Days [Member] | Commercial [Member] | Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	364	3,425
RE Mortgage [Member] | > 90 Days [Member] | Commercial [Member] | PNCI Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total past due	$ 80	$ 748