Quarterly report pursuant to Section 13 or 15(d)

LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Narrative) (Details)

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LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Narrative) (Details)
3 Months Ended 12 Months Ended
Mar. 31, 2024
USD ($)
segment
loan
Mar. 31, 2023
USD ($)
Dec. 31, 2023
USD ($)
Dec. 31, 2022
USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Nonaccrual loans, interest income $ 0   $ 0  
Loans under modified terms   $ 20,541,000    
Total Allowance for credit losses 136,190,000 116,512,000 132,182,000 $ 110,768,000
Transfer from LHFI to LHFS $ 0 7,087,000    
Number of operating segments | segment 2      
Loans held for investment, accrued interest receivable $ 72,800,000   $ 72,500,000  
Financing Receivable Accrued Interest After Allowance For Credit Loss Statement Of Financial Position Extensible List Not Disclosed (Flag) true   true  
Commercial Portfolio        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Total Allowance for credit losses $ 110,528,000 88,086,000 $ 105,896,000 $ 82,753,000
Troubled Loan Modifications        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Unfunded commitments on TLM loans 1,100,000 4,400,000    
TLM loans that went into default $ 1,000,000.0      
Troubled Loan Modifications | Past Due        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Number of loans designated as TLMS currently past due | loan 3      
TLMs that are past due $ 3,400,000 $ 0