FAIR VALUE (Financial Assets and Liabilities at Dates Indicated that Were Accounted for or Disclosed at Fair Value) (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	$ 1,357,205	$ 1,073,333
Residential mortgage loans held for sale (at fair value)	88,728	53,701
Residential Mortgage Loans Held For Sale
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Residential mortgage loans held for sale (at fair value)	85,800	52,600
U.S. treasuries and government agencies
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	139,405	258,495
State and municipal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	352,987	233,649
Mortgage-backed and asset-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	852,314	570,759
Corporate debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	12,499	9,552
Trust preferred
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	310
Debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	1,357,205	1,072,765
Marketable equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	568
Fair Value, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	1,357,205	1,073,333
Total assets	1,456,156	1,129,541
Total liabilities	(10,223)	(2,507)
Fair Value, Recurring | Residential Mortgage Loans Held For Sale
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Residential mortgage loans held for sale	88,728	53,701
Fair Value, Recurring | U.S. treasuries and government agencies
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	139,405	258,495
Fair Value, Recurring | State and municipal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	352,987	233,649
Fair Value, Recurring | Mortgage-backed and asset-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	852,314	570,759
Fair Value, Recurring | Corporate debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	12,499	9,552
Fair Value, Recurring | Trust preferred
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)		310
Fair Value, Recurring | Debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)		1,072,765
Fair Value, Recurring | Marketable equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)		568
Fair Value, Recurring | Interest rate swap agreements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements	10,223	2,507
Interest rate swap agreements	(10,223)	(2,507)
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Total assets	0	0
Total liabilities	0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Residential Mortgage Loans Held For Sale
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Residential mortgage loans held for sale	0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. treasuries and government agencies
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | State and municipal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage-backed and asset-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Trust preferred
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)		0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)		0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Marketable equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)		0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate swap agreements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements	0	0
Interest rate swap agreements	0	0
Fair Value, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	1,344,706	1,063,471
Total assets	1,443,657	1,119,679
Total liabilities	(10,223)	(2,507)
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Residential Mortgage Loans Held For Sale
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Residential mortgage loans held for sale	88,728	53,701
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | U.S. treasuries and government agencies
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	139,405	258,495
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | State and municipal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	352,987	233,649
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Mortgage-backed and asset-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	852,314	570,759
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Corporate debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Trust preferred
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)		0
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)		1,062,903
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Marketable equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)		568
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Interest rate swap agreements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements	10,223	2,507
Interest rate swap agreements	(10,223)	(2,507)
Fair Value, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	12,499	9,862
Total assets	12,499	9,862
Total liabilities	0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Residential Mortgage Loans Held For Sale
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Residential mortgage loans held for sale	0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | U.S. treasuries and government agencies
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | State and municipal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Mortgage-backed and asset-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Corporate debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	12,499	9,552
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Trust preferred
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)		310
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)		9,862
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Marketable equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)		0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Interest rate swap agreements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements	0	0
Interest rate swap agreements	$ 0	$ 0