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Basis of Accounting and Consolidation - Additional Information (Details)
 3 Months Ended 12 Months Ended
Mar. 20, 2023
USD ($)
$ / shares
shares
Sep. 30, 2024
USD ($)
Jun. 30, 2024
USD ($)
Dec. 31, 2024
USD ($)
Segment
$ / shares
shares
Dec. 31, 2023
USD ($)
$ / shares
shares
Dec. 31, 2022
USD ($)
shares
Dec. 31, 2021
USD ($)
Summary Of Significant Accounting Policies [Line Items]              
Common stock, par value (in dollars per share) | $ / shares       $ 4 $ 4    
Number of operating segment | Segment       1      
Assets       $ 7,519,734,000 $ 7,586,794,000    
Loans       5,595,666,000 5,506,910,000    
Deposits       $ 6,057,096,000 6,123,659,000    
Federal funds selling period       1 day      
Intangible assets amortization period       15 years      
Captive maximum gross premiums       $ 2,800,000      
Value of trust accounts       $ 6,400,000,000 $ 6,100,000,000    
Stock plans, term       10 years      
Maximum number of shares to be issued in stock incentive plan (in shares) | shares       550,000      
RSA/RSU, grants in period, gross | shares       80,332 45,986 63,150  
Employee discount for employee stock purchase plan       15.00%      
Employee stock purchase plan, number of shares authorized | shares       600,000      
Stock issued during period, shares, employee stock purchase plans | shares       32,936 38,989 23,055  
Right of use lease assets       $ 13,861,000 $ 14,306,000    
Lease liability       14,190,000 14,615,000    
Cumulative change in accounting principal       846,391,000 793,204,000 $ 633,155,000 $ 633,894,000
Allowance for credit losses on loans       $ 70,182,000 $ 68,675,000 $ 59,093,000 $ 54,655,000
Employee Stock Purchase Plan              
Summary Of Significant Accounting Policies [Line Items]              
Shares available for issuance | shares       473,336      
Minimum              
Summary Of Significant Accounting Policies [Line Items]              
Certificates of deposit investments original maturities period       3 years      
Maximum              
Summary Of Significant Accounting Policies [Line Items]              
Certificates of deposit investments original maturities period       5 years      
Mid Rivers Insurance Group, Inc.              
Summary Of Significant Accounting Policies [Line Items]              
Purchase price   $ 10,100,000          
Purdum, Gray, Ingledue, Beck, Inc.              
Summary Of Significant Accounting Policies [Line Items]              
Purchase price     $ 10,200,000        
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) | $ / shares $ 0.01            
Share Price | $ / shares $ 4            
Consideration payable in cash $ 2,000            
Consideration payable in shares | shares 3,290,222            
Conversion of common stock | shares 1.15            
Common stock consideration value $ 93,508,000            
Purchase price $ 93,510,000