CREDIT QUALITY ASSESSMENT (Activity in Allowance for Loan and Lease Losses by Respective Loan Portfolio Segment) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year			$ 44,067	$ 40,895	$ 40,895
Provision (credit)	$ 934	$ 781	2,450	4,974	5,546
Charge-offs			(2,044)	(2,586)	(3,134)
Recoveries			451	659	760
Net charge-offs			(1,593)	(1,927)	(2,374)
Balance at period end	44,924	$ 43,942	44,924	43,942	44,067
Total loans and leases	$ 4,194,118		$ 4,194,118		$ 3,927,808
Allowance for loans and leases to total loans and leases ratio	1.07%		1.07%		1.12%
Balance of loans specifically evaluated for impairment	$ 22,513		$ 22,513		$ 24,092
Allowance for loans specifically evaluated for impairment	$ 4,770		$ 4,770		$ 4,825
Specific allowance to specific loans ratio	21.19%		21.19%		20.03%
Balance of loans collectively evaluated	$ 4,171,605		$ 4,171,605		$ 3,903,716
Allowance for loans collectively evaluated	40,154		$ 40,154		$ 39,242
Collective allowance to collective loans ratio			0.96%		1.01%
Commercial
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year			$ 7,539	6,529	$ 6,529
Provision (credit)			2,552		1,563
Charge-offs			(1,469)		(597)
Recoveries			73		44
Net charge-offs			(1,396)		(553)
Balance at period end	8,695		8,695		7,539
Total loans and leases	$ 451,667		$ 451,667		$ 467,286
Allowance for loans and leases to total loans and leases ratio	1.93%		1.93%		1.61%
Balance of loans specifically evaluated for impairment	$ 8,403		$ 8,403		$ 7,018
Allowance for loans specifically evaluated for impairment	$ 3,841		$ 3,841		$ 2,604
Specific allowance to specific loans ratio	45.71%		45.71%		37.10%
Balance of loans collectively evaluated	$ 443,264		$ 443,264		$ 460,268
Allowance for loans collectively evaluated	4,854		$ 4,854		$ 4,935
Collective allowance to collective loans ratio			1.10%		1.07%
Consumer
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year			$ 2,828	3,456	$ 3,456
Provision (credit)			147		112
Charge-offs			(560)		(888)
Recoveries			101		148
Net charge-offs			(459)		(740)
Balance at period end	2,516		2,516		2,828
Total loans and leases	$ 456,395		$ 456,395		$ 456,657
Allowance for loans and leases to total loans and leases ratio	0.55%		0.55%		0.62%
Balance of loans collectively evaluated	$ 456,395		$ 456,395		$ 456,657
Allowance for loans collectively evaluated	2,516		$ 2,516		$ 2,828
Collective allowance to collective loans ratio			0.55%		0.62%
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year			$ 4,652	4,691	$ 4,691
Provision (credit)			(829)		(31)
Charge-offs			0		(48)
Recoveries			103		40
Net charge-offs			103		(8)
Balance at period end	3,926		3,926		4,652
Total loans and leases	$ 295,222		$ 295,222		$ 308,279
Allowance for loans and leases to total loans and leases ratio	1.33%		1.33%		1.51%
Balance of loans specifically evaluated for impairment	$ 137		$ 137		$ 137
Allowance for loans specifically evaluated for impairment	$ 0		$ 0		$ 0
Specific allowance to specific loans ratio	0.00%		0.00%		0.00%
Balance of loans collectively evaluated	$ 295,085		$ 295,085		$ 308,142
Allowance for loans collectively evaluated	3,926		$ 3,926		$ 4,652
Collective allowance to collective loans ratio			1.33%		1.51%
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year			$ 12,939	10,440	$ 10,440
Provision (credit)			1,230		2,563
Charge-offs			0		(197)
Recoveries			93		133
Net charge-offs			93		(64)
Balance at period end	14,262		14,262		12,939
Total loans and leases	$ 1,104,669		$ 1,104,669		$ 928,113
Allowance for loans and leases to total loans and leases ratio	1.29%		1.29%		1.39%
Balance of loans specifically evaluated for impairment	$ 5,589		$ 5,589		$ 8,107
Allowance for loans specifically evaluated for impairment	$ 589		$ 589		$ 1,736
Specific allowance to specific loans ratio	10.54%		10.54%		21.41%
Balance of loans collectively evaluated	$ 1,099,080		$ 1,099,080		$ 920,006
Allowance for loans collectively evaluated	13,673		$ 13,673		$ 11,203
Collective allowance to collective loans ratio			1.24%		1.22%
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year			$ 7,885	7,984	$ 7,984
Provision (credit)			(481)		(104)
Charge-offs			(5)		0
Recoveries			0		5
Net charge-offs			(5)		5
Balance at period end	7,399		7,399		7,885
Total loans and leases	$ 831,461		$ 831,461		$ 775,552
Allowance for loans and leases to total loans and leases ratio	0.89%		0.89%		1.02%
Balance of loans specifically evaluated for impairment	$ 5,517		$ 5,517		$ 5,567
Allowance for loans specifically evaluated for impairment	$ 340		$ 340		$ 485
Specific allowance to specific loans ratio	6.16%		6.16%		8.71%
Balance of loans collectively evaluated	$ 825,944		$ 825,944		$ 769,985
Allowance for loans collectively evaluated	7,059		$ 7,059		$ 7,400
Collective allowance to collective loans ratio			0.85%		0.96%
Residential Real Estate Portfolio Segment | Residential Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year			$ 7,261	6,901	$ 6,901
Provision (credit)			(241)		1,406
Charge-offs			(10)		(1,404)
Recoveries			61		358
Net charge-offs			51		(1,046)
Balance at period end	7,071		7,071		7,261
Total loans and leases	$ 882,890		$ 882,890		$ 841,692
Allowance for loans and leases to total loans and leases ratio	0.80%		0.80%		0.86%
Balance of loans specifically evaluated for impairment	$ 2,867		$ 2,867		$ 3,263
Allowance for loans specifically evaluated for impairment	0		0		0
Balance of loans collectively evaluated	880,023		880,023		838,429
Allowance for loans collectively evaluated	7,071		$ 7,071		$ 7,261
Collective allowance to collective loans ratio			0.80%		0.87%
Residential Real Estate Portfolio Segment | Residential Construction
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of year			$ 963	$ 894	$ 894
Provision (credit)			72		37
Charge-offs			0		0
Recoveries			20		32
Net charge-offs			20		32
Balance at period end	1,055		1,055		963
Total loans and leases	$ 171,814		$ 171,814		$ 150,229
Allowance for loans and leases to total loans and leases ratio	0.61%		0.61%		0.64%
Balance of loans specifically evaluated for impairment	$ 0		$ 0		$ 0
Allowance for loans specifically evaluated for impairment	0		0		0
Balance of loans collectively evaluated	171,814		171,814		150,229
Allowance for loans collectively evaluated	$ 1,055		$ 1,055		$ 963
Collective allowance to collective loans ratio			0.61%		0.64%