Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUE MEASUREMENTS (Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis) (Details)

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FAIR VALUE MEASUREMENTS (Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis) (Details) - USD ($)
$ in Thousands
Mar. 31, 2021
Dec. 31, 2020
ASSETS    
Securities available for sale, at fair value $ 2,697,043 $ 2,540,419
Loans held for sale, at fair value 49,082 96,742
Fair value hedges 2,139  
LIABILITIES    
Cash flow hedges 1,808  
Fair value hedges 7,949 12,483
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 2,697,043 2,540,419
Loans held for sale, at fair value 49,082 96,742
Fair value hedges 2,139  
LIABILITIES    
Cash flow hedges 1,808  
Fair value hedges 7,949 12,483
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 49,082 96,742
Fair value hedges 2,139  
LIABILITIES    
Cash flow hedges 1,808  
Fair value hedges 7,949 12,483
Recurring | Quoted Prices in Active Markets for Identical Assets Level 1    
ASSETS    
Loans held for sale, at fair value 0 0
Fair value hedges 0  
LIABILITIES    
Cash flow hedges 0  
Fair value hedges 0 0
Recurring | Significant Other Observable Inputs Level 2    
ASSETS    
Loans held for sale, at fair value 49,082 96,742
Fair value hedges 2,139  
LIABILITIES    
Cash flow hedges 1,808  
Fair value hedges 7,949 12,483
Recurring | Significant Unobservable Inputs Level 3    
ASSETS    
Loans held for sale, at fair value 0 0
Fair value hedges 0  
LIABILITIES    
Cash flow hedges 0  
Fair value hedges 0 0
U.S. government and agency securities    
ASSETS    
Securities available for sale, at fair value 11,677 13,394
U.S. government and agency securities | Recurring    
ASSETS    
Securities available for sale, at fair value 11,677 13,394
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 11,677 13,394
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 899,098 837,326
Obligations of states and political subdivisions | Recurring    
ASSETS    
Securities available for sale, at fair value 899,098 837,326
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 899,098 837,326
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 147,608 151,078
Corporate and other bonds | Recurring    
ASSETS    
Securities available for sale, at fair value 147,608 151,078
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 147,608 151,078
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 1,637,035 1,536,996
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 1,637,035 1,536,996
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 1,625
Other securities | Recurring    
ASSETS    
Securities available for sale, at fair value 1,625 1,625
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 1,625
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 106,450 163,360
LIABILITIES    
Interest rate swap 106,450 163,360
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 106,450 163,360
LIABILITIES    
Interest rate swap 106,450 163,360
Interest Rate Swap | Significant Unobservable Inputs Level 3    
ASSETS    
Interest rate swap 0 0
LIABILITIES    
Interest rate swap 0 0
Interest Rate Swap | Recurring    
ASSETS    
Interest rate swap 106,450 163,360
LIABILITIES    
Interest rate swap 106,450 163,360
Interest Rate Swap | Recurring | 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 | Recurring | Significant Other Observable Inputs Level 2    
ASSETS    
Interest rate swap 106,450 163,360
LIABILITIES    
Interest rate swap 106,450 163,360
Interest Rate Swap | Recurring | Significant Unobservable Inputs Level 3    
ASSETS    
Interest rate swap 0 0
LIABILITIES    
Interest rate swap $ 0 $ 0