v3.21.2
BORROWINGS (Details)
9 Months Ended 12 Months Ended
Sep. 30, 2021
USD ($)
Institution
Dec. 31, 2017
USD ($)
Dec. 31, 2020
USD ($)
Debt Instrument [Line Items]      
Overnight FHLB advances     $ 255,000,000
Long-term line of credit $ 0    
Loans pledged as collateral 3,800,000,000    
Federal Home Loan Bank, maximum borrowing capacity 2,500,000,000    
Federal Home Loan Bank, additional credit available 275,000,000    
Unsecured debt $ 195,000,000    
Number of financial institutions | Institution 5    
Unused lines of credit $ 2,900,000,000   2,400,000,000
FHLB, average daily balance of borrowings outstanding     56,000,000
Secured debt 204,000,000    
Minimum      
Debt Instrument [Line Items]      
Unsecured debt 20,000,000    
Maximum      
Debt Instrument [Line Items]      
Unsecured debt 100,000,000    
Revolving Credit Facility      
Debt Instrument [Line Items]      
Line of credit, borrowing capacity   $ 40,000,000  
Line of credit maturity period   5 years  
Revolving Credit Facility | 90 Day LIBOR      
Debt Instrument [Line Items]      
Debt instrument basis point rate   3.50%  
FFI      
Debt Instrument [Line Items]      
Long-term line of credit $ 12,500,000   $ 14,000,000
Line of credit facility, Interest rate 3.64%