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LOANS AND CREDIT QUALITY - Amortized Cost in Loans Based Upon Year of Origination and Payment Status (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024 | Dec. 31, 2024
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract] |  |  |  |  |
Total loan and lease receivables before allowance for credit losses | $ 14,568,795 |  | $ 14,568,795 |  | $ 9,643,497
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract] |  |  |  |  |
Loans and leases charged off during the period | 12,803 | $ 14,572 | 34,969 | $ 46,034 |
Residential Real Estate |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract] |  |  |  |  |
Financing receivable, year one | 412,755 |  | 412,755 |  | 235,132
Financing receivable, year two | 176,598 |  | 176,598 |  | 97,522
Financing receivable, year three | 116,483 |  | 116,483 |  | 456,174
Financing receivable, year four | 783,083 |  | 783,083 |  | 608,721
Financing receivable, more than four years |  |  |  |  | 812,936
Financing receivable, year five | 835,953 |  | 835,953 |  |
Financing receivable, more than five years | 1,082,148 |  | 1,082,148 |  |
Revolving Loans Amortized Cost Basis | 494,769 |  | 494,769 |  | 70,478
Revolving Loans Converted to Term | 5,312 |  | 5,312 |  | 0
Total loan and lease receivables before allowance for credit losses | 3,907,101 |  | 3,907,101 |  | 2,280,963
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract] |  |  |  |  |
Financing receivable, year one, Gross charge-offs |  |  | 0 |  | 0
Financing receivable, year two, Gross charge-offs |  |  | 0 |  | 0
Financing receivable, year three, Gross charge-offs |  |  | 0 |  | 0
Financing receivable, year four, Gross charge-offs |  |  | 0 |  | 0
Financing receivable, Gross charge-offs more than four years |  |  |  |  | 10
Financing receivable, year five, Gross charge-offs |  |  | 0 |  |
Financing receivable, more than five years, Gross charge-offs |  |  | 9 |  |
Revolving Loans Amortized Cost Basis |  |  | 0 |  | 0
Revolving Loans Converted to Term |  |  | 0 |  | 0
Loans and leases charged off during the period | 9 | 0 | 9 | 10 | 10
Residential Real Estate | Performing |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract] |  |  |  |  |
Financing receivable, year one | 412,755 |  | 412,755 |  | 235,132
Financing receivable, year two | 176,598 |  | 176,598 |  | 97,522
Financing receivable, year three | 116,483 |  | 116,483 |  | 456,174
Financing receivable, year four | 782,678 |  | 782,678 |  | 608,721
Financing receivable, more than four years |  |  |  |  | 810,899
Financing receivable, year five | 835,953 |  | 835,953 |  |
Financing receivable, more than five years | 1,077,996 |  | 1,077,996 |  |
Revolving Loans Amortized Cost Basis | 491,871 |  | 491,871 |  | 69,661
Revolving Loans Converted to Term | 5,171 |  | 5,171 |  | 0
Total loan and lease receivables before allowance for credit losses | 3,899,505 |  | 3,899,505 |  | 2,278,109
Residential Real Estate | Nonperforming |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract] |  |  |  |  |
Financing receivable, year one | 0 |  | 0 |  | 0
Financing receivable, year two | 0 |  | 0 |  | 0
Financing receivable, year three | 0 |  | 0 |  | 0
Financing receivable, year four | 405 |  | 405 |  | 0
Financing receivable, more than four years |  |  |  |  | 2,037
Financing receivable, year five | 0 |  | 0 |  |
Financing receivable, more than five years | 4,152 |  | 4,152 |  |
Revolving Loans Amortized Cost Basis | 2,898 |  | 2,898 |  | 817
Revolving Loans Converted to Term | 141 |  | 141 |  | 0
Total loan and lease receivables before allowance for credit losses | 7,596 |  | 7,596 |  | 2,854
Auto |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract] |  |  |  |  |
Financing receivable, year one | 165 |  | 165 |  | 0
Financing receivable, year two | 260 |  | 260 |  | 81,494
Financing receivable, year three | 56,358 |  | 56,358 |  | 834,757
Financing receivable, year four | 547,809 |  | 547,809 |  | 499,076
Financing receivable, more than four years |  |  |  |  | 181,608
Financing receivable, year five | 284,655 |  | 284,655 |  |
Financing receivable, more than five years | 65,368 |  | 65,368 |  |
Revolving Loans Amortized Cost Basis | 0 |  | 0 |  | 0
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total loan and lease receivables before allowance for credit losses | 954,615 |  | 954,615 |  | 1,596,935
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract] |  |  |  |  |
Financing receivable, year one, Gross charge-offs |  |  | 0 |  | 0
Financing receivable, year two, Gross charge-offs |  |  | 0 |  | 2,223
Financing receivable, year three, Gross charge-offs |  |  | 1,325 |  | 29,978
Financing receivable, year four, Gross charge-offs |  |  | 18,657 |  | 16,780
Financing receivable, Gross charge-offs more than four years |  |  |  |  | 6,116
Financing receivable, year five, Gross charge-offs |  |  | 9,744 |  |
Financing receivable, more than five years, Gross charge-offs |  |  | 2,399 |  |
Revolving Loans Amortized Cost Basis |  |  | 0 |  | 0
Revolving Loans Converted to Term |  |  | 0 |  | 0
Loans and leases charged off during the period | 11,365 | 13,318 | 32,125 | 42,850 | 55,097
Auto | Performing |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract] |  |  |  |  |
Financing receivable, year one | 165 |  | 165 |  | 0
Financing receivable, year two | 260 |  | 260 |  | 81,178
Financing receivable, year three | 56,105 |  | 56,105 |  | 831,402
Financing receivable, year four | 544,758 |  | 544,758 |  | 497,176
Financing receivable, more than four years |  |  |  |  | 180,927
Financing receivable, year five | 283,351 |  | 283,351 |  |
Financing receivable, more than five years | 64,989 |  | 64,989 |  |
Revolving Loans Amortized Cost Basis | 0 |  | 0 |  | 0
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total loan and lease receivables before allowance for credit losses | 949,628 |  | 949,628 |  | 1,590,683
Auto | Nonperforming |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract] |  |  |  |  |
Financing receivable, year one | 0 |  | 0 |  | 0
Financing receivable, year two | 0 |  | 0 |  | 316
Financing receivable, year three | 253 |  | 253 |  | 3,355
Financing receivable, year four | 3,051 |  | 3,051 |  | 1,900
Financing receivable, more than four years |  |  |  |  | 681
Financing receivable, year five | 1,304 |  | 1,304 |  |
Financing receivable, more than five years | 379 |  | 379 |  |
Revolving Loans Amortized Cost Basis | 0 |  | 0 |  | 0
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total loan and lease receivables before allowance for credit losses | 4,987 |  | 4,987 |  | 6,252
Other consumer |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract] |  |  |  |  |
Financing receivable, year one | 160,340 |  | 160,340 |  | 167,162
Financing receivable, year two | 172,040 |  | 172,040 |  | 136,903
Financing receivable, year three | 145,144 |  | 145,144 |  | 71,023
Financing receivable, year four | 72,037 |  | 72,037 |  | 22,414
Financing receivable, more than four years |  |  |  |  | 38,429
Financing receivable, year five | 16,992 |  | 16,992 |  |
Financing receivable, more than five years | 29,841 |  | 29,841 |  |
Revolving Loans Amortized Cost Basis | 5,945 |  | 5,945 |  | 2,920
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total loan and lease receivables before allowance for credit losses | 602,339 |  | 602,339 |  | 438,851
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract] |  |  |  |  |
Financing receivable, year one, Gross charge-offs |  |  | 450 |  | 700
Financing receivable, year two, Gross charge-offs |  |  | 1 |  | 0
Financing receivable, year three, Gross charge-offs |  |  | 0 |  | 0
Financing receivable, year four, Gross charge-offs |  |  | 0 |  | 950
Financing receivable, Gross charge-offs more than four years |  |  |  |  | 1,521
Financing receivable, year five, Gross charge-offs |  |  | 511 |  |
Financing receivable, more than five years, Gross charge-offs |  |  | 868 |  |
Revolving Loans Amortized Cost Basis |  |  | 50 |  | 47
Revolving Loans Converted to Term |  |  | 0 |  | 0
Loans and leases charged off during the period | 695 | $ 941 | 1,880 | $ 2,649 | 3,218
Other consumer | Performing |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract] |  |  |  |  |
Financing receivable, year one | 160,340 |  | 160,340 |  | 167,162
Financing receivable, year two | 172,039 |  | 172,039 |  | 136,903
Financing receivable, year three | 145,144 |  | 145,144 |  | 71,023
Financing receivable, year four | 72,037 |  | 72,037 |  | 22,414
Financing receivable, more than four years |  |  |  |  | 38,429
Financing receivable, year five | 16,992 |  | 16,992 |  |
Financing receivable, more than five years | 29,841 |  | 29,841 |  |
Revolving Loans Amortized Cost Basis | 5,938 |  | 5,938 |  | 2,919
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total loan and lease receivables before allowance for credit losses | 602,331 |  | 602,331 |  | 438,850
Other consumer | Nonperforming |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract] |  |  |  |  |
Financing receivable, year one | 0 |  | 0 |  | 0
Financing receivable, year two | 1 |  | 1 |  | 0
Financing receivable, year three | 0 |  | 0 |  | 0
Financing receivable, year four | 0 |  | 0 |  | 0
Financing receivable, more than four years |  |  |  |  | 0
Financing receivable, year five | 0 |  | 0 |  |
Financing receivable, more than five years | 0 |  | 0 |  |
Revolving Loans Amortized Cost Basis | 7 |  | 7 |  | 1
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total loan and lease receivables before allowance for credit losses | $ 8 |  | $ 8 |  | $ 1

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