FAIR VALUE MEASUREMENTS (Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
ASSETS
Securities available for sale, at fair value	$ 2,540,419	$ 1,945,445
Loans held for sale, at fair value	96,742	55,405
Fair value hedges		182
LIABILITIES
Cash flow hedges		1,147
Fair value hedges	12,483	6,256
Quoted Prices in Active Markets for Identical Assets Level 1
ASSETS
Securities available for sale, at fair value	0	0
Loans held for sale, at fair value	0	0
Fair value hedges		0
LIABILITIES
Cash flow hedges		0
Fair value hedges	0	0
Significant Other Observable Inputs Level 2
ASSETS
Securities available for sale, at fair value	2,540,419	1,945,445
Loans held for sale, at fair value	96,742	55,405
Fair value hedges		182
LIABILITIES
Cash flow hedges		1,147
Fair value hedges	12,483	6,256
Significant Unobservable Inputs Level 3
ASSETS
Securities available for sale, at fair value	0	0
Loans held for sale, at fair value	0	0
Fair value hedges		0
LIABILITIES
Cash flow hedges		0
Fair value hedges	0	0
Recurring
ASSETS
Loans held for sale, at fair value	96,742	55,405
Interest rate swap	163,360	54,345
Fair value hedges		182
LIABILITIES
Interest rate swap	163,360	54,345
Cash flow hedges		1,147
Fair value hedges	12,483	6,256
Recurring \| Quoted Prices in Active Markets for Identical Assets Level 1
ASSETS
Loans held for sale, at fair value	0	0
Interest rate swap	0	0
Fair value hedges		0
LIABILITIES
Interest rate swap	0	0
Cash flow hedges		0
Fair value hedges	0	0
Recurring \| Significant Other Observable Inputs Level 2
ASSETS
Loans held for sale, at fair value	96,742	55,405
Interest rate swap	163,360	54,345
Fair value hedges		182
LIABILITIES
Interest rate swap	163,360	54,345
Cash flow hedges		1,147
Fair value hedges	12,483	6,256
Recurring \| Significant Unobservable Inputs Level 3
ASSETS
Loans held for sale, at fair value	0	0
Interest rate swap	0	0
Fair value hedges		0
LIABILITIES
Interest rate swap	0	0
Cash flow hedges		0
Fair value hedges	0	0
U.S. government and agency securities
ASSETS
Securities available for sale, at fair value	13,394	21,320
U.S. government and agency securities \| Recurring
ASSETS
Securities available for sale, at fair value	13,394	21,320
U.S. government and agency securities \| Recurring \| Quoted Prices in Active Markets for Identical Assets Level 1
ASSETS
Securities available for sale, at fair value	0	0
U.S. government and agency securities \| Recurring \| Significant Other Observable Inputs Level 2
ASSETS
Securities available for sale, at fair value	13,394	21,320
U.S. government and agency securities \| Recurring \| Significant Unobservable Inputs Level 3
ASSETS
Securities available for sale, at fair value	0	0
Obligations of states and political subdivisions
ASSETS
Securities available for sale, at fair value	837,326	447,091
Obligations of states and political subdivisions \| Recurring
ASSETS
Securities available for sale, at fair value	837,326	447,091
Obligations of states and political subdivisions \| Recurring \| Quoted Prices in Active Markets for Identical Assets Level 1
ASSETS
Securities available for sale, at fair value	0	0
Obligations of states and political subdivisions \| Recurring \| Significant Other Observable Inputs Level 2
ASSETS
Securities available for sale, at fair value	837,326	447,091
Obligations of states and political subdivisions \| Recurring \| Significant Unobservable Inputs Level 3
ASSETS
Securities available for sale, at fair value	0	0
Corporate and other bonds
ASSETS
Securities available for sale, at fair value	151,078	135,959
Corporate and other bonds \| Recurring
ASSETS
Securities available for sale, at fair value	151,078	135,959
Corporate and other bonds \| Recurring \| Quoted Prices in Active Markets for Identical Assets Level 1
ASSETS
Securities available for sale, at fair value	0	0
Corporate and other bonds \| Recurring \| Significant Other Observable Inputs Level 2
ASSETS
Securities available for sale, at fair value	151,078	135,959
Corporate and other bonds \| Recurring \| Significant Unobservable Inputs Level 3
ASSETS
Securities available for sale, at fair value	0	0
Total mortgage-back securities \| Recurring
ASSETS
Securities available for sale, at fair value	1,536,996	1,337,996
Total mortgage-back securities \| Recurring \| Quoted Prices in Active Markets for Identical Assets Level 1
ASSETS
Securities available for sale, at fair value	0	0
Total mortgage-back securities \| Recurring \| Significant Other Observable Inputs Level 2
ASSETS
Securities available for sale, at fair value	1,536,996	1,337,996
Total mortgage-back securities \| Recurring \| Significant Unobservable Inputs Level 3
ASSETS
Securities available for sale, at fair value	0	0
Other securities
ASSETS
Securities available for sale, at fair value	1,625	3,079
Other securities \| Recurring
ASSETS
Securities available for sale, at fair value	1,625	3,079
Other securities \| Recurring \| Quoted Prices in Active Markets for Identical Assets Level 1
ASSETS
Securities available for sale, at fair value	0	0
Other securities \| Recurring \| Significant Other Observable Inputs Level 2
ASSETS
Securities available for sale, at fair value	1,625	3,079
Other securities \| Recurring \| Significant Unobservable Inputs Level 3
ASSETS
Securities available for sale, at fair value	0	0
Interest Rate Swap
ASSETS
Interest rate swap	163,360	54,345
LIABILITIES
Interest rate swap	163,360	54,345
Interest Rate Swap \| Quoted Prices in Active Markets for Identical Assets Level 1
ASSETS
Interest rate swap	0	0
LIABILITIES
Interest rate swap	0	0
Interest Rate Swap \| Significant Other Observable Inputs Level 2
ASSETS
Interest rate swap	163,360	54,345
LIABILITIES
Interest rate swap	163,360	54,345
Interest Rate Swap \| Significant Unobservable Inputs Level 3
ASSETS
Interest rate swap	0	0
LIABILITIES
Interest rate swap	$ 0	$ 0

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Fair value of all liability derivatives designated as cash flow hedging instruments.

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