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Basis of Accounting and Consolidation - Additional Information (Details) - USD ($)
 3 Months Ended
Mar. 21, 2023
Feb. 14, 2022
Mar. 31, 2023
Mar. 31, 2022
Dec. 31, 2022
Summary Of Significant Accounting Policies [Line Items]          
Common stock, par value (in dollars per share)     $ 4   $ 4
Deposits     $ 5,030,778,000   $ 5,257,001,000
Stock plans, term     10 years    
Maximum number of shares to be issued in stock incentive plan (in shares)     399,983    
Employee discount for employee stock purchase plan     15.00%    
Employee stock purchase plan, number of shares authorized     600,000    
Stock issued during period, shares, employee stock purchase plans     7,963 3,149  
Captive maximum gross premiums     $ 2,650,000    
Stock Options          
Summary Of Significant Accounting Policies [Line Items]          
Common stock awarded in SI plan (in shares)     0    
Restricted Stock          
Summary Of Significant Accounting Policies [Line Items]          
Common stock awarded in SI plan (in shares)     60,550 26,000  
Restricted Stock Units (RSUs)          
Summary Of Significant Accounting Policies [Line Items]          
Common stock awarded in SI plan (in shares)     37,900 37,150  
Blackhawk Bancorp, Inc          
Summary Of Significant Accounting Policies [Line Items]          
Percentage of issued and outstanding shares acquired 100.00%        
Common stock, par value (in dollars per share) $ 0.01        
Conversion of common stock 1.15        
Share Price $ 4.00        
Consideration payable in shares 3,330,176        
Delta Bancshares Company          
Summary Of Significant Accounting Policies [Line Items]          
Percentage of issued and outstanding shares acquired   100.00%      
Common stock, par value (in dollars per share)   $ 10.00      
Share Price   $ 4.00      
Consideration payable in cash   $ 15,150,000      
Consideration payable in shares   2,292,270