CREDIT QUALITY ASSESSMENT (Credit Risk Rating Indicators for Each Segment of Commercial Loan Portfolio) (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 6,569,990	$ 6,571,634
Commercial
Financing Receivable Recorded Investment [Line Items]
Total loans	769,660	796,264
Commercial Portfolio Segment [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	4,638,191	4,638,763
Commercial Portfolio Segment [Member] | Commercial
Financing Receivable Recorded Investment [Line Items]
Total loans	769,660	796,264
Commercial Portfolio Segment [Member] | Pass
Financing Receivable Recorded Investment [Line Items]
Total loans	4,579,731	4,576,321
Commercial Portfolio Segment [Member] | Pass | Commercial
Financing Receivable Recorded Investment [Line Items]
Total loans	747,335	773,958
Commercial Portfolio Segment [Member] | Special Mention
Financing Receivable Recorded Investment [Line Items]
Total loans	6,602	8,827
Commercial Portfolio Segment [Member] | Special Mention | Commercial
Financing Receivable Recorded Investment [Line Items]
Total loans	2,162	1,942
Commercial Portfolio Segment [Member] | Substandard [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	51,858	53,615
Commercial Portfolio Segment [Member] | Substandard [Member] | Commercial
Financing Receivable Recorded Investment [Line Items]
Total loans	20,163	20,364
Commercial Portfolio Segment [Member] | Doubtful
Financing Receivable Recorded Investment [Line Items]
Total loans	0	0
Commercial Portfolio Segment [Member] | Doubtful | Commercial
Financing Receivable Recorded Investment [Line Items]
Total loans	0	0
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction
Financing Receivable Recorded Investment [Line Items]
Total loans	688,939	681,201
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans	1,962,879	1,958,395
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans	1,216,713	1,202,903
Commercial Real Estate Portfolio Segment | Pass | Commercial Acquisition, Development and Construction
Financing Receivable Recorded Investment [Line Items]
Total loans	685,313	677,574
Commercial Real Estate Portfolio Segment | Pass | Commercial Investor Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans	1,942,814	1,934,886
Commercial Real Estate Portfolio Segment | Pass | Commercial Owner Occupied Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans	1,204,269	1,189,903
Commercial Real Estate Portfolio Segment | Special Mention | Commercial Acquisition, Development and Construction
Financing Receivable Recorded Investment [Line Items]
Total loans	320	321
Commercial Real Estate Portfolio Segment | Special Mention | Commercial Investor Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans	1,980	3,826
Commercial Real Estate Portfolio Segment | Special Mention | Commercial Owner Occupied Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans	2,140	2,738
Commercial Real Estate Portfolio Segment | Substandard [Member] | Commercial Acquisition, Development and Construction
Financing Receivable Recorded Investment [Line Items]
Total loans	3,306	3,306
Commercial Real Estate Portfolio Segment | Substandard [Member] | Commercial Investor Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans	18,085	19,683
Commercial Real Estate Portfolio Segment | Substandard [Member] | Commercial Owner Occupied Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans	10,304	10,262
Commercial Real Estate Portfolio Segment | Doubtful | Commercial Acquisition, Development and Construction
Financing Receivable Recorded Investment [Line Items]
Total loans	0	0
Commercial Real Estate Portfolio Segment | Doubtful | Commercial Investor Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans	0	0
Commercial Real Estate Portfolio Segment | Doubtful | Commercial Owner Occupied Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 0	$ 0