Credit Quality Assessment (Activity in Allowance for Loan and Lease Losses by Respective Loan Portfolio Segment) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year				$ 37,802				$ 38,766	$ 37,802	$ 38,766	$ 42,957
Provision (credit)	$ 1,850	$ 1,706	$ 1,218	597	$ 853	$ (192)	$ 158	(982)	5,371	(163)	(1,084)
Charge-offs									(3,795)	(2,687)	(11,165)
Recoveries									1,517	1,886	8,058
Net charge-offs									(2,278)	(801)	(3,107)
Balance at period end	40,895				37,802				40,895	37,802	38,766
Total loans and leases	$ 3,495,370				$ 3,127,392				$ 3,495,370	$ 3,127,392
Allowance for loans and leases to total loans and leases ratio	1.17%				1.21%				1.17%	1.21%
Balance of loans specifically evaluated for impairment	$ 28,927				$ 29,419				$ 28,927	$ 29,419
Allowance for loans specifically evaluated for impairment	$ 3,375				$ 2,894				$ 3,375	$ 2,894	3,058
Specific allowance to specific loans ratio	11.67%				9.84%				11.67%	9.84%
Balance of loans collectively evaluated	$ 3,466,443				$ 3,097,973				$ 3,466,443	$ 3,097,973
Allowance for loans collectively evaluated	37,520				34,908				$ 37,520	$ 34,908	35,708
Collective allowance to collective loans ratio									1.08%	1.13%
Commercial
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year				5,852				6,308	$ 5,852	$ 6,308
Provision (credit)									508	(1,204)
Charge-offs									(306)	(729)
Recoveries									475	1,477
Net charge-offs									169	748
Balance at period end	6,529				5,852				6,529	5,852	6,308
Total loans and leases	$ 465,765				$ 390,781				$ 465,765	$ 390,781
Allowance for loans and leases to total loans and leases ratio	1.40%				1.50%				1.40%	1.50%
Balance of loans specifically evaluated for impairment	$ 5,273				$ 3,894				$ 5,273	$ 3,894
Allowance for loans specifically evaluated for impairment	$ 1,318				$ 788				$ 1,318	$ 788
Specific allowance to specific loans ratio	25.00%				20.24%				25.00%	20.24%
Balance of loans collectively evaluated	$ 460,492				$ 386,887				$ 460,492	$ 386,887
Allowance for loans collectively evaluated	5,211				5,064				$ 5,211	$ 5,064
Collective allowance to collective loans ratio									1.13%	1.31%
Leases
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year				9				16	$ 9	$ 16
Provision (credit)									(5)	(7)
Charge-offs									(4)	0
Recoveries									0	0
Net charge-offs									(4)	0
Balance at period end	0				9				0	9	16
Total loans and leases	0				$ 54				0	$ 54
Allowance for loans and leases to total loans and leases ratio					16.80%					16.80%
Balance of loans collectively evaluated					$ 54					$ 54
Allowance for loans collectively evaluated					9					$ 9
Collective allowance to collective loans ratio										16.80%
Consumer
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year				3,592				4,142	3,592	$ 4,142
Provision (credit)									619	119
Charge-offs									(998)	(834)
Recoveries									243	165
Net charge-offs									(755)	(669)
Balance at period end	3,456				3,592				3,456	3,592	4,142
Total loans and leases	$ 450,875				$ 425,552				$ 450,875	$ 425,552
Allowance for loans and leases to total loans and leases ratio	0.77%				0.84%				0.77%	0.84%
Balance of loans collectively evaluated	$ 450,875				$ 425,552				$ 450,875	$ 425,552
Allowance for loans collectively evaluated	3,456				3,592				$ 3,456	$ 3,592
Collective allowance to collective loans ratio									0.77%	0.84%
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year				4,267				3,754	$ 4,267	$ 3,754
Provision (credit)									583	1,042
Charge-offs									(739)	(529)
Recoveries									580	0
Net charge-offs									(159)	(529)
Balance at period end	4,691				4,267				4,691	4,267	3,754
Total loans and leases	$ 255,980				$ 205,124				$ 255,980	$ 205,124
Allowance for loans and leases to total loans and leases ratio	1.83%				2.08%				1.83%	2.08%
Balance of loans specifically evaluated for impairment	$ 194				$ 2,464				$ 194	$ 2,464
Allowance for loans specifically evaluated for impairment	$ 58				$ 741				$ 58	$ 741
Specific allowance to specific loans ratio	29.90%				30.07%				29.90%	30.07%
Balance of loans collectively evaluated	$ 255,786				$ 202,660				$ 255,786	$ 202,660
Allowance for loans collectively evaluated	4,633				3,526				$ 4,633	$ 3,526
Collective allowance to collective loans ratio									1.81%	1.74%
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year				9,784				9,263	$ 9,784	$ 9,263
Provision (credit)									727	486
Charge-offs									(91)	(3)
Recoveries									20	38
Net charge-offs									(71)	35
Balance at period end	10,440				9,784				10,440	9,784	9,263
Total loans and leases	$ 719,084				$ 640,193				$ 719,084	$ 640,193
Allowance for loans and leases to total loans and leases ratio	1.45%				1.53%				1.45%	1.53%
Balance of loans specifically evaluated for impairment	$ 10,441				$ 10,279				$ 10,441	$ 10,279
Allowance for loans specifically evaluated for impairment	$ 1,489				$ 541				$ 1,489	$ 541
Specific allowance to specific loans ratio	14.26%				5.26%				14.26%	5.26%
Balance of loans collectively evaluated	$ 708,643				$ 629,914				$ 708,643	$ 629,914
Allowance for loans collectively evaluated	8,951				9,243				$ 8,951	$ 9,243
Collective allowance to collective loans ratio									1.26%	1.47%
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year				7,143				6,308	$ 7,143	$ 6,308
Provision (credit)									1,881	1,094
Charge-offs									(1,043)	(265)
Recoveries									3	6
Net charge-offs									(1,040)	(259)
Balance at period end	7,984				7,143				7,984	7,143	6,308
Total loans and leases	$ 678,027				$ 611,061				$ 678,027	$ 611,061
Allowance for loans and leases to total loans and leases ratio	1.18%				1.17%				1.18%	1.17%
Balance of loans specifically evaluated for impairment	$ 6,580				$ 8,941				$ 6,580	$ 8,941
Allowance for loans specifically evaluated for impairment	$ 510				$ 824				$ 510	$ 824
Specific allowance to specific loans ratio	7.75%				9.22%				7.75%	9.22%
Balance of loans collectively evaluated	$ 671,447				$ 602,120				$ 671,447	$ 602,120
Allowance for loans collectively evaluated	7,474				6,319				$ 7,474	$ 6,319
Collective allowance to collective loans ratio									1.11%	1.05%
Residential Real Estate Portfolio Segment | Residential Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year				6,232				7,819	$ 6,232	$ 7,819
Provision (credit)									1,138	(1,385)
Charge-offs									(614)	(323)
Recoveries									145	121
Net charge-offs									(469)	(202)
Balance at period end	6,901				6,232				6,901	6,232	7,819
Total loans and leases	$ 796,358				$ 717,886				$ 796,358	$ 717,886
Allowance for loans and leases to total loans and leases ratio	0.87%				0.87%				0.87%	0.87%
Balance of loans specifically evaluated for impairment	$ 6,439				$ 3,535				$ 6,439	$ 3,535
Allowance for loans specifically evaluated for impairment	0				0				0	0
Balance of loans collectively evaluated	789,919				714,351				789,919	714,351
Allowance for loans collectively evaluated	6,901				6,232				$ 6,901	$ 6,232
Collective allowance to collective loans ratio									0.87%	0.87%
Residential Real Estate Portfolio Segment | Residential Construction
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year				$ 923				$ 1,156	$ 923	$ 1,156
Provision (credit)									(80)	(308)
Charge-offs									0	(4)
Recoveries									51	79
Net charge-offs									51	75
Balance at period end	894				923				894	923	$ 1,156
Total loans and leases	$ 129,281				$ 136,741				$ 129,281	$ 136,741
Allowance for loans and leases to total loans and leases ratio	0.69%				0.67%				0.69%	0.67%
Balance of loans specifically evaluated for impairment	$ 0				$ 306				$ 0	$ 306
Allowance for loans specifically evaluated for impairment	0				0				0	0
Balance of loans collectively evaluated	129,281				136,435				129,281	136,435
Allowance for loans collectively evaluated	$ 894				$ 923				$ 894	$ 923
Collective allowance to collective loans ratio									0.69%	0.68%