Credit Quality Assessment (Activity in Allowance for Loan and Lease Losses by Respective Loan Portfolio Segment) (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year	$ 37,802	$ 38,766	$ 38,766
Provision (credit)	3,521		(163)
Charge-offs	(2,753)		(2,687)
Loan and lease recoveries	1,091	1,365	1,886
Net charge-offs	(1,662)	(176)	(801)
Balance at period end	39,661	37,574	37,802
Total loans and leases	$ 3,412,439		$ 3,127,392
Allowance for loans and leases to total loans and leases ratio	1.16%		1.21%
Balance of loans specifically evaluated for impairment	$ 30,905		$ 29,419
Allowance for loans specifically evaluated for impairment	$ 3,002		$ 2,894
Specific allowance to specific loans ratio	9.71%		9.84%
Balance of loans collectively evaluated	$ 3,381,534		$ 3,097,973
Allowance for loans collectively evaluated	$ 36,659		$ 34,908
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	$ 6,308
Provision (credit)	139		(1,204)
Charge-offs	(185)		(729)
Loan and lease recoveries	226		1,477
Net charge-offs	41		748
Balance at period end	6,032		5,852
Total loans and leases	$ 423,855		$ 390,781
Allowance for loans and leases to total loans and leases ratio	1.42%		1.50%
Balance of loans specifically evaluated for impairment	$ 5,360		$ 3,894
Allowance for loans specifically evaluated for impairment	$ 1,278		$ 788
Specific allowance to specific loans ratio	23.84%		20.24%
Balance of loans collectively evaluated	$ 418,495		$ 386,887
Allowance for loans collectively evaluated	$ 4,754		$ 5,064
Collective allowance to collective loans ratio	1.14%		1.31%
Leases
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year	$ 9	16	$ 16
Provision (credit)	0		(7)
Charge-offs	0		0
Loan and lease recoveries	0		0
Net charge-offs	0		0
Balance at period end	9		9
Total loans and leases	$ 19		$ 54
Allowance for loans and leases to total loans and leases ratio	47.37%		16.80%
Balance of loans collectively evaluated	$ 19		$ 54
Allowance for loans collectively evaluated	$ 9		$ 9
Collective allowance to collective loans ratio	47.37%		16.80%
Consumer
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year	$ 3,592	4,142	$ 4,142
Provision (credit)	881		119
Charge-offs	(930)		(834)
Loan and lease recoveries	144		165
Net charge-offs	(786)		(669)
Balance at period end	3,687		3,592
Total loans and leases	$ 444,729		$ 425,552
Allowance for loans and leases to total loans and leases ratio	0.83%		0.84%
Balance of loans collectively evaluated	$ 444,729		$ 425,552
Allowance for loans collectively evaluated	$ 3,687		$ 3,592
Collective allowance to collective loans ratio	0.83%		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	$ 3,754
Provision (credit)	293		1,042
Charge-offs	(739)		(529)
Loan and lease recoveries	580		0
Net charge-offs	(159)		(529)
Balance at period end	4,401		4,267
Total loans and leases	$ 239,160		$ 205,124
Allowance for loans and leases to total loans and leases ratio	1.84%		2.08%
Balance of loans specifically evaluated for impairment	$ 194		$ 2,464
Allowance for loans specifically evaluated for impairment	$ 57		$ 741
Specific allowance to specific loans ratio	29.38%		30.07%
Balance of loans collectively evaluated	$ 238,966		$ 202,660
Allowance for loans collectively evaluated	$ 4,344		$ 3,526
Collective allowance to collective loans ratio	1.82%		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	$ 9,263
Provision (credit)	68		486
Charge-offs	(90)		(3)
Loan and lease recoveries	15		38
Net charge-offs	(75)		35
Balance at period end	9,777		9,784
Total loans and leases	$ 710,694		$ 640,193
Allowance for loans and leases to total loans and leases ratio	1.38%		1.53%
Balance of loans specifically evaluated for impairment	$ 10,697		$ 10,279
Allowance for loans specifically evaluated for impairment	$ 709		$ 541
Specific allowance to specific loans ratio	6.63%		5.26%
Balance of loans collectively evaluated	$ 699,997		$ 629,914
Allowance for loans collectively evaluated	$ 9,068		$ 9,243
Collective allowance to collective loans ratio	1.30%		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	$ 6,308
Provision (credit)	1,218		1,094
Charge-offs	(317)		(265)
Loan and lease recoveries	2		6
Net charge-offs	(315)		(259)
Balance at period end	8,046		7,143
Total loans and leases	$ 680,601		$ 611,061
Allowance for loans and leases to total loans and leases ratio	1.18%		1.17%
Balance of loans specifically evaluated for impairment	$ 8,172		$ 8,941
Allowance for loans specifically evaluated for impairment	$ 958		$ 824
Specific allowance to specific loans ratio	11.72%		9.22%
Balance of loans collectively evaluated	$ 672,429		$ 602,120
Allowance for loans collectively evaluated	$ 7,088		$ 6,319
Collective allowance to collective loans ratio	1.05%		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	$ 7,819
Provision (credit)	919		(1,385)
Charge-offs	(492)		(323)
Loan and lease recoveries	103		121
Net charge-offs	(389)		(202)
Balance at period end	6,762		6,232
Total loans and leases	$ 773,889		$ 717,886
Allowance for loans and leases to total loans and leases ratio	0.87%		0.87%
Balance of loans specifically evaluated for impairment	$ 6,482		$ 3,535
Allowance for loans specifically evaluated for impairment	0		0
Balance of loans collectively evaluated	767,407		714,351
Allowance for loans collectively evaluated	$ 6,762		$ 6,232
Collective allowance to collective loans ratio	0.88%		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	$ 1,156
Provision (credit)	3		(308)
Charge-offs	0		(4)
Loan and lease recoveries	21		79
Net charge-offs	21		75
Balance at period end	947		923
Total loans and leases	$ 139,492		$ 136,741
Allowance for loans and leases to total loans and leases ratio	0.68%		0.67%
Balance of loans specifically evaluated for impairment			$ 306
Allowance for loans specifically evaluated for impairment			0
Balance of loans collectively evaluated	$ 139,492		136,435
Allowance for loans collectively evaluated	$ 947		$ 923
Collective allowance to collective loans ratio	0.68%		0.68%

Reflects the percentage derived from dividing total credit loss allowance by total loans.

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Financing Receivable, Allowance for Credit Losses, Net Charge Offs

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Percentage of credit loss allowance to loans for loans collectively evaluated for impairment.

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Percentage of credit loss allowance for loans specifically evaluated for impairment.

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A valuation allowance for financing receivables that are expected to be uncollectible.

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of recovery of financing receivables doubtful of collection that were previously charged off.

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Amount of direct write-downs of financing receivables charged against the allowance.

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- Definition

Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

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