CREDIT QUALITY ASSESSMENT (Activity in Allowance for Credit Losses or Loan Losses by Respective Loan Portfolio Segment) (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	$ 56,132,000	$ 53,486,000	$ 53,486,000
Provision (credit)	24,469,000	(128,000)	4,684,000
Charge-offs	(654,000)	(356,000)	(2,668,000)
Recoveries	108,000	87,000	630,000
Net charge-offs	(546,000)	(269,000)	(2,038,000)
Balance at end of period	85,800,000	53,089,000	56,132,000
Total loans	$ 6,722,992,000		$ 6,705,232,000
Allowance for loan losses to total loans ratio	1.28%		0.84%
Balance of loans individually evaluated for credit loss	$ 37,675,000		$ 24,773,000
Balance of loans specifically evaluated for impairment			24,773,000
Allowance related to loans evaluated individually	$ 8,643,000		5,501,000
Allowance for loans specifically evaluated for impairment			$ 5,501,000
Individual allowance to loans evaluated individually ratio	22.94%
Specific allowance to specific loans ratio			22.21%
Balance of loans collectively evaluated for credit loss	$ 6,685,317,000
Balance of loans collectively evaluated			$ 6,667,375,000
Allowance related to loans evaluated collectively	$ 77,157,000		50,631,000
Allowance for loans collectively evaluated			$ 50,631,000
Collective allowance to collective loans ratio	1.15%		0.76%
Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance of loans acquired			$ 13,084,000
Allowance for loans acquired			$ 0
Allowance to loans acquired with deteriorated credity quality ratio			0.00%
Initial allowance on purchased credit deteriorated loans at adoption of ASC 326 [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	$ 2,762,000	0	$ 0
Balance at end of period			2,762,000
Transition impact of adopting ASC 326 [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	2,983,000	0	0
Balance at end of period			2,983,000
Commercial [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	11,395,000	11,377,000	11,377,000
Provision (credit)	13,506,000		1,164,000
Charge-offs	(175,000)		(1,195,000)
Recoveries	67,000		49,000
Net charge-offs	(108,000)		(1,146,000)
Balance at end of period	29,330,000		11,395,000
Total loans	$ 813,525,000		$ 801,019,000
Allowance for loan losses to total loans ratio	3.61%		1.42%
Balance of loans individually evaluated for credit loss	$ 11,560,000
Balance of loans specifically evaluated for impairment			$ 8,867,000
Allowance related to loans evaluated individually	$ 5,659,000
Allowance for loans specifically evaluated for impairment			$ 3,817,000
Individual allowance to loans evaluated individually ratio	48.95%
Specific allowance to specific loans ratio			43.05%
Balance of loans collectively evaluated for credit loss	$ 801,965,000
Balance of loans collectively evaluated			$ 789,613,000
Allowance related to loans evaluated collectively	$ 23,671,000
Allowance for loans collectively evaluated			$ 7,578,000
Collective allowance to collective loans ratio	2.95%		0.96%
Commercial [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance of loans acquired			$ 2,539,000
Allowance for loans acquired			$ 0
Allowance to loans acquired with deteriorated credity quality ratio			0.00%
Commercial [Member] | Initial allowance on purchased credit deteriorated loans at adoption of ASC 326 [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	$ 1,549,000
Balance at end of period			$ 1,549,000
Commercial [Member] | Transition impact of adopting ASC 326 [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	2,988,000
Balance at end of period			2,988,000
Consumer
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	2,086,000	2,113,000	2,113,000
Provision (credit)	1,349,000		565,000
Charge-offs	(133,000)		(783,000)
Recoveries	26,000		191,000
Net charge-offs	(107,000)		(592,000)
Balance at end of period	4,247,000		2,086,000
Total loans	$ 453,346,000		$ 466,764,000
Allowance for loan losses to total loans ratio	0.94%		0.45%
Balance of loans individually evaluated for credit loss	$ 1,313,000
Allowance related to loans evaluated individually	$ 99,000
Individual allowance to loans evaluated individually ratio	7.54%
Balance of loans collectively evaluated for credit loss	$ 452,033,000
Balance of loans collectively evaluated			$ 465,771,000
Allowance related to loans evaluated collectively	$ 4,148,000
Allowance for loans collectively evaluated			$ 2,086,000
Collective allowance to collective loans ratio	0.92%		0.45%
Consumer | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance of loans acquired			$ 993,000
Allowance for loans acquired			$ 0
Allowance to loans acquired with deteriorated credity quality ratio			0.00%
Consumer | Initial allowance on purchased credit deteriorated loans at adoption of ASC 326 [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	$ 99,000
Balance at end of period			$ 99,000
Consumer | Transition impact of adopting ASC 326 [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	820,000
Balance at end of period			820,000
Commercial Real Estate Portfolio Segment | Commercial AD&C [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	7,590,000	5,944,000	5,944,000
Provision (credit)	1,042,000		1,418,000
Charge-offs	0		0
Recoveries	0		228,000
Net charge-offs	0		228,000
Balance at end of period	11,208,000		7,590,000
Total loans	$ 643,114,000		$ 684,010,000
Allowance for loan losses to total loans ratio	1.74%		1.11%
Balance of loans individually evaluated for credit loss	$ 829,000
Balance of loans specifically evaluated for impairment			$ 829,000
Allowance related to loans evaluated individually	$ 132,000
Allowance for loans specifically evaluated for impairment			$ 132,000
Individual allowance to loans evaluated individually ratio	15.92%
Specific allowance to specific loans ratio			0.00%
Balance of loans collectively evaluated for credit loss	$ 642,285,000
Balance of loans collectively evaluated			$ 683,181,000
Allowance related to loans evaluated collectively	$ 11,076,000
Allowance for loans collectively evaluated			$ 7,458,000
Collective allowance to collective loans ratio	1.72%		1.09%
Commercial Real Estate Portfolio Segment | Commercial AD&C [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance of loans acquired			$ 0
Allowance for loans acquired			$ 0
Allowance to loans acquired with deteriorated credity quality ratio			0.00%
Commercial Real Estate Portfolio Segment | Commercial AD&C [Member] | Initial allowance on purchased credit deteriorated loans at adoption of ASC 326 [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	$ 0
Balance at end of period			$ 0
Commercial Real Estate Portfolio Segment | Commercial AD&C [Member] | Transition impact of adopting ASC 326 [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	2,576,000
Balance at end of period			2,576,000
Commercial Real Estate Portfolio Segment | Commercial Investor RE [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	18,407,000	17,603,000	17,603,000
Provision (credit)	3,454,000		788,000
Charge-offs	0		0
Recoveries	0		16,000
Net charge-offs	0		16,000
Balance at end of period	19,850,000		18,407,000
Total loans	$ 2,241,240,000		$ 2,169,156,000
Allowance for loan losses to total loans ratio	0.89%		0.85%
Balance of loans individually evaluated for credit loss	$ 18,545,000
Balance of loans specifically evaluated for impairment			$ 9,212,000
Allowance related to loans evaluated individually	$ 2,704,000
Allowance for loans specifically evaluated for impairment			$ 1,529,000
Individual allowance to loans evaluated individually ratio	14.58%
Specific allowance to specific loans ratio			16.60%
Balance of loans collectively evaluated for credit loss	$ 2,222,695,000
Balance of loans collectively evaluated			$ 2,150,400,000
Allowance related to loans evaluated collectively	$ 17,146,000
Allowance for loans collectively evaluated			$ 16,878,000
Collective allowance to collective loans ratio	0.77%		0.78%
Commercial Real Estate Portfolio Segment | Commercial Investor RE [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance of loans acquired			$ 9,544,000
Allowance for loans acquired			$ 0
Allowance to loans acquired with deteriorated credity quality ratio			0.00%
Commercial Real Estate Portfolio Segment | Commercial Investor RE [Member] | Initial allowance on purchased credit deteriorated loans at adoption of ASC 326 [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	$ 1,114,000
Balance at end of period			$ 1,114,000
Commercial Real Estate Portfolio Segment | Commercial Investor RE [Member] | Transition impact of adopting ASC 326 [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	(3,125,000)
Balance at end of period			(3,125,000)
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied RE [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	6,884,000	6,307,000	6,307,000
Provision (credit)	2,839,000		577,000
Charge-offs	0		0
Recoveries	0		0
Net charge-offs	0		0
Balance at end of period	10,110,000		6,884,000
Total loans	$ 1,305,682,000		$ 1,288,677,000
Allowance for loan losses to total loans ratio	0.77%		0.53%
Balance of loans individually evaluated for credit loss	$ 4,074,000
Balance of loans specifically evaluated for impairment			$ 4,148,000
Allowance related to loans evaluated individually	$ 49,000
Allowance for loans specifically evaluated for impairment			$ 23,000
Individual allowance to loans evaluated individually ratio	1.20%
Specific allowance to specific loans ratio			0.55%
Balance of loans collectively evaluated for credit loss	$ 1,301,608,000
Balance of loans collectively evaluated			$ 1,284,529,000
Allowance related to loans evaluated collectively	$ 10,061,000
Allowance for loans collectively evaluated			$ 6,861,000
Collective allowance to collective loans ratio	0.77%		0.53%
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied RE [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance of loans acquired			$ 0
Allowance for loans acquired			$ 0
Allowance to loans acquired with deteriorated credity quality ratio			0.00%
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied RE [Member] | Initial allowance on purchased credit deteriorated loans at adoption of ASC 326 [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	$ 0
Balance at end of period			$ 0
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied RE [Member] | Transition impact of adopting ASC 326 [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	387,000
Balance at end of period			387,000
Residential Real Estate Portfolio Segment | Residential Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	8,803,000	8,881,000	8,881,000
Provision (credit)	1,810,000		474,000
Charge-offs	(346,000)		(690,000)
Recoveries	13,000		138,000
Net charge-offs	(333,000)		(552,000)
Balance at end of period	9,892,000		8,803,000
Total loans	$ 1,116,512,000		$ 1,149,327,000
Allowance for loan losses to total loans ratio	0.89%		0.77%
Balance of loans individually evaluated for credit loss	$ 1,354,000
Balance of loans specifically evaluated for impairment			$ 1,717,000
Allowance related to loans evaluated individually	$ 0
Allowance for loans specifically evaluated for impairment			$ 0
Individual allowance to loans evaluated individually ratio	0.00%
Specific allowance to specific loans ratio			0.00%
Balance of loans collectively evaluated for credit loss	$ 1,115,158,000
Balance of loans collectively evaluated			$ 1,147,602,000
Allowance related to loans evaluated collectively	$ 9,892,000
Allowance for loans collectively evaluated			$ 8,803,000
Collective allowance to collective loans ratio	0.89%		0.77%
Residential Real Estate Portfolio Segment | Residential Mortgage | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance of loans acquired			$ 8,000
Allowance for loans acquired			$ 0
Allowance to loans acquired with deteriorated credity quality ratio			0.00%
Residential Real Estate Portfolio Segment | Residential Mortgage | Initial allowance on purchased credit deteriorated loans at adoption of ASC 326 [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	$ 0
Balance at end of period			$ 0
Residential Real Estate Portfolio Segment | Residential Mortgage | Transition impact of adopting ASC 326 [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	(388,000)
Balance at end of period			(388,000)
Residential Real Estate Portfolio Segment | Residential Construction
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	967,000	$ 1,261,000	1,261,000
Provision (credit)	469,000		(302,000)
Charge-offs	0		0
Recoveries	2,000		8,000
Net charge-offs	2,000		8,000
Balance at end of period	1,163,000		967,000
Total loans	$ 149,573,000		$ 146,279,000
Allowance for loan losses to total loans ratio	0.78%		0.66%
Balance of loans individually evaluated for credit loss	$ 0
Balance of loans specifically evaluated for impairment			$ 0
Allowance related to loans evaluated individually	$ 0
Allowance for loans specifically evaluated for impairment			$ 0
Individual allowance to loans evaluated individually ratio	0.00%
Specific allowance to specific loans ratio			0.00%
Balance of loans collectively evaluated for credit loss	$ 149,573,000
Balance of loans collectively evaluated			$ 146,279,000
Allowance related to loans evaluated collectively	$ 1,163,000
Allowance for loans collectively evaluated			$ 967,000
Collective allowance to collective loans ratio	0.78%		0.66%
Residential Real Estate Portfolio Segment | Residential Construction | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance of loans acquired			$ 0
Allowance for loans acquired			$ 0
Allowance to loans acquired with deteriorated credity quality ratio			0.00%
Residential Real Estate Portfolio Segment | Residential Construction | Initial allowance on purchased credit deteriorated loans at adoption of ASC 326 [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	$ 0
Balance at end of period			$ 0
Residential Real Estate Portfolio Segment | Residential Construction | Transition impact of adopting ASC 326 [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	$ (275,000)
Balance at end of period			$ (275,000)