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Commitments and Contingencies - Schedule of Financial Instruments with Off-Balance Sheet Risk (Details) - USD ($) $ in Thousands | Dec. 31, 2025 | Dec. 31, 2024
--- | --- | ---
Loan Commitments [Line Items] |  |
Unadvanced portion of loans and leases | $ 2,483,239 | $ 1,076,783
Unused lines of credit: |  |
Home equity | 1,175,702 | 780,214
Other consumer | 148,358 | 113,838
Other commercial | 0 | 398
Unused letters of credit: |  |
Financial standby letters of credit | 10,440 | 12,702
Performance standby letters of credit | 25,025 | 24,325
Commercial and similar letters of credit | 58,074 | 2,330
Interest rate derivatives |  |
Unused letters of credit: |  |
Notional Amount | 192,468 | 225,000
Receive fixed, pay variable |  |
Unused letters of credit: |  |
Notional Amount | 3,505,840 | 1,672,948
Pay fixed, receive variable |  |
Unused letters of credit: |  |
Notional Amount | 3,505,840 | 1,672,948
Risk participation-out agreements |  |
Unused letters of credit: |  |
Notional Amount | 670,834 | 539,731
Risk participation-in agreements |  |
Unused letters of credit: |  |
Notional Amount | 153,185 | 102,198
Foreign exchange contracts | Buys foreign currency, sells U.S. currency |  |
Unused letters of credit: |  |
Notional Amount | 2,785 | 5,849
Foreign exchange contracts | Sells foreign currency, buys U.S. currency |  |
Unused letters of credit: |  |
Notional Amount | 2,800 | 5,408
Commercial real estate |  |
Loan Commitments [Line Items] |  |
Commitments to originate loans and leases | 99,457 | 11,126
Commercial |  |
Loan Commitments [Line Items] |  |
Commitments to originate loans and leases | 137,923 | 144,721
Residential mortgage |  |
Loan Commitments [Line Items] |  |
Commitments to originate loans and leases | 23,115 | 14,607
Home equity |  |
Loan Commitments [Line Items] |  |
Commitments to originate loans and leases | $ 9,022 | $ 0

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