v3.26.3
BUSINESS COMBINATION - Additional Information (Details)
$ in Thousands
 3 Months Ended 9 Months Ended
Jan. 01, 2026
USD ($)
shares
Nov. 01, 2025
USD ($)
Jun. 23, 2025
USD ($)
shares
Sep. 30, 2026
USD ($)
shares
Mar. 31, 2026
USD ($)
Sep. 30, 2025
USD ($)
Sep. 30, 2026
USD ($)
shares
Sep. 30, 2025
USD ($)
Jun. 30, 2026
USD ($)
numberOfOffices
Dec. 31, 2025
USD ($)
Jun. 30, 2025
USD ($)
Dec. 31, 2024
USD ($)
Business Combination [Line Items]                        
Assets       $ 22,314,155     $ 22,314,155     $ 21,129,379    
Net loans and leases       13,713,432     13,713,432     13,237,583    
Deposits       17,697,791     17,697,791     16,421,842    
Business Combination, Recognized Liability Assumed, Liability           $ 0   $ 0        
Gain on bargain purchase       37   0 12,118 0        
Financing Receivable, Purchased with Credit Deterioration, Amount at Par Value $ 3,964 $ 31,957                    
Financing Receivable, Purchased with Credit Deterioration, Allowance for Credit Loss at Acquisition Date 785 3,050                    
Financing Receivable, Purchased with Credit Deterioration, Amount at Purchase Price 3,081 27,402                    
Less: Allowance for credit losses       $ 191,650   $ 161,916 $ 191,650 $ 161,916 $ 189,912 186,487 $ 158,522 $ 156,791
Finward Bancorp                        
Business Combination [Line Items]                        
Assets                 2,000,000      
Deposits                 $ 1,700,000      
Business combination, Consideration Transferred, Equity interest Issued Ratio | shares       1.35     1.35          
Number of banking offices | numberOfOffices                 24      
Loans, net of ACL                 $ 1,500,000      
BankFinancial                        
Business Combination [Line Items]                        
Assets 1,400,000                      
Deposits $ 1,300,000                      
Business Combination, Consideration Transferred, Equity Interest, Share Issued, Number of Shares | shares 5,980,878                      
Business Combination, Consideration Transferred, Equity Interest $ 149,648                      
Cash consideration 6                      
Business Combination, Recognized Asset Acquired, Asset 1,413,632                      
Business Combination, Recognized Liability Assumed, Liability $ 1,251,860     $ 1,251,860     $ 1,251,860          
Goodwill       5,700     21,500          
Business combination, Consideration Transferred, Equity interest Issued Ratio | shares 0.48                      
Gain on bargain purchase $ 12,118           12,118          
Financing Receivable, Purchased with Credit Deterioration, Amount at Par Value 4,000                      
Financing Receivable, Purchased with Credit Deterioration, Allowance for Credit Loss at Acquisition Date 800                      
Financing Receivable, Purchased with Credit Deterioration, Amount at Purchase Price 3,000                      
Business Combination, Consideration Transferred 149,654                      
Less: Allowance for credit losses 2,800                 $ 2,829    
Loans, net of ACL $ 264,098                      
Westfield Bank                        
Business Combination [Line Items]                        
Assets       2,100,000     2,100,000          
Deposits       1,900,000     1,900,000          
Business Combination, Consideration Transferred, Equity Interest, Share Issued, Number of Shares | shares     2,753,094                  
Business Combination, Consideration Transferred, Equity Interest   64,450 $ 64,400                  
Cash consideration   260,000 260,000                  
Payments for Merger Related Costs       1,200 $ 5,800   12,200          
Business Combination, Recognized Asset Acquired, Asset   2,128,227                    
Business Combination, Recognized Liability Assumed, Liability       $ 87     $ 87          
Goodwill   92,280                    
Business Combination, Price of Acquisition, Expected     $ 324,400                  
Financing Receivable, Purchased with Credit Deterioration, Amount at Par Value   32,000                    
Financing Receivable, Purchased with Credit Deterioration, Allowance for Credit Loss at Acquisition Date   3,000                    
Financing Receivable, Purchased with Credit Deterioration, Amount at Purchase Price   27,400                    
Business Combination, Consideration Transferred   324,450                    
Less: Allowance for credit losses   23,700                    
Loans, net of ACL   $ 1,571,298