v3.26.1
Loans and Allowance for Credit Losses Allowance for Loan Losses by Portfolio Segment (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Allowance for Loan and Lease Losses [Roll Forward]          
Beginning balance $ 367,489 $ 379,677 $ 364,462 $ 379,156 $ 379,156
Loans charged off (26,010) (15,916) (44,328) (35,950)  
Recoveries of loans previously charged off 3,994 4,202 7,404 11,645  
Net loans (charged off) recovered (22,016) (11,714) (36,924) (24,305)  
Provision for credit losses 4,897 8,607 19,339 22,505  
Ending balance 382,580 377,337 382,580 377,337 364,462
Loans - Excluding OBS Credit Exposure          
Allowance for Loan and Lease Losses [Roll Forward]          
Beginning balance 367,489 379,677 364,462 379,156 379,156
Initial allowance for credit losses on purchased loans 30,993   34,344    
Loans charged off (26,010) (15,916) (44,328) (35,950)  
Recoveries of loans previously charged off 3,994 4,202 7,404 11,645  
Net loans (charged off) recovered (22,016) (11,714) (36,924) (24,305)  
Provision for credit losses 6,308 9,374 20,892 22,486  
Other (194)   (194)    
Ending balance 382,580 377,337 382,580 377,337 364,462
Loans - Excluding OBS Credit Exposure | Real estate - commercial mortgage          
Allowance for Loan and Lease Losses [Roll Forward]          
Beginning balance 159,042 162,146 157,302 158,181 158,181
Initial allowance for credit losses on purchased loans 19,993   22,771    
Loans charged off (10,789) (6,402) (14,891) (18,508)  
Recoveries of loans previously charged off 1,629 133 2,330 507  
Net loans (charged off) recovered (9,160) (6,269) (12,561) (18,001)  
Provision for credit losses (1,641) (2,494) 722 13,203  
Other 0   0    
Ending balance 168,234 153,383 168,234 153,383 157,302
Loans - Excluding OBS Credit Exposure | Commercial and Industrial          
Allowance for Loan and Lease Losses [Roll Forward]          
Beginning balance 78,978 96,851 77,740 92,212 92,212
Initial allowance for credit losses on purchased loans 5,622   6,116    
Loans charged off (12,015) (5,780) (22,560) (9,645)  
Recoveries of loans previously charged off 1,280 2,628 2,020 8,580  
Net loans (charged off) recovered (10,735) (3,152) (20,540) (1,065)  
Provision for credit losses 3,006 3,821 13,555 6,373  
Other (194)   (194)    
Ending balance 76,677 97,520 76,677 97,520 77,740
Loans - Excluding OBS Credit Exposure | Real estate - residential mortgage          
Allowance for Loan and Lease Losses [Roll Forward]          
Beginning balance 89,860 82,416 88,961 81,331 81,331
Initial allowance for credit losses on purchased loans 4,915   4,915    
Loans charged off (121) (258) (512) (601)  
Recoveries of loans previously charged off 197 203 268 377  
Net loans (charged off) recovered 76 (55) (244) (224)  
Provision for credit losses 729 (5) 1,948 1,249  
Other 0   0    
Ending balance 95,580 82,356 95,580 82,356 88,961
Loans - Excluding OBS Credit Exposure | Consumer and Real Estate - Home Equity          
Allowance for Loan and Lease Losses [Roll Forward]          
Beginning balance 24,194 19,294 23,026 19,397 19,397
Initial allowance for credit losses on purchased loans 288   288    
Loans charged off (2,119) (1,885) (4,284) (4,078)  
Recoveries of loans previously charged off 484 899 1,068 1,559  
Net loans (charged off) recovered (1,635) (986) (3,216) (2,519)  
Provision for credit losses 3,077 1,173 5,826 2,603  
Other 0   0    
Ending balance 25,924 19,481 25,924 19,481 23,026
Loans - Excluding OBS Credit Exposure | Real estate - construction          
Allowance for Loan and Lease Losses [Roll Forward]          
Beginning balance 9,353 15,900 10,896 25,140 25,140
Initial allowance for credit losses on purchased loans 175   254    
Loans charged off 0 (100) 0 (100)  
Recoveries of loans previously charged off 0 99 884 181  
Net loans (charged off) recovered 0 (1) 884 81  
Provision for credit losses 630 4,837 (1,876) (4,485)  
Other 0   0    
Ending balance 10,158 20,736 10,158 20,736 10,896
Loans - Excluding OBS Credit Exposure | Leases and other loans          
Allowance for Loan and Lease Losses [Roll Forward]          
Beginning balance 6,062 3,070 6,537 2,895 2,895
Initial allowance for credit losses on purchased loans 0   0    
Loans charged off (966) (1,491) (2,081) (3,018)  
Recoveries of loans previously charged off 404 240 834 441  
Net loans (charged off) recovered (562) (1,251) (1,247) (2,577)  
Provision for credit losses 507 2,042 717 3,543  
Other 0   0    
Ending balance $ 6,007 $ 3,861 $ 6,007 $ 3,861 $ 6,537