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LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES (Narrative) (Details) |  | 3 Months Ended | 6 Months Ended | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Jun. 26, 2025 USD ($) | Jun. 30, 2025 USD ($) | Jun. 30, 2024 USD ($) | Jun. 30, 2025 USD ($) segment | Jun. 30, 2024 USD ($) | Dec. 31, 2024 USD ($) | Apr. 01, 2025 USD ($) | Mar. 31, 2025 USD ($) | Mar. 31, 2024 USD ($) | Dec. 31, 2023 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |  |  |
Gain on CRE loan sale |  |  |  | $ 15,720,000 | $ 0 |  |  |  |  |
Nonaccrual loans, interest income |  | $ 0 | $ 0 | 0 | 0 |  |  |  |  |
Loans under modified terms |  | 18,091,000 | 23,920,000 | 20,232,000 | 24,096,000 |  |  |  |  |
Amortized Cost |  | 18,091,000 | 23,920,000 | 20,232,000 | 24,096,000 |  |  |  |  |
Total Allowance for credit losses |  | 315,574,000 | 158,131,000 | 315,574,000 | 158,131,000 | $ 178,644,000 |  | $ 193,796,000 | $ 136,190,000 | $ 132,182,000
Unfunded commitments on loans modified and designated as TLMs |  | 0 |  | 0 |  |  |  |  |  |
TLM loans that went into default |  | 0 | 0 | 0 | 0 |  |  |  |  |
TLMs that are past due |  | 0 | 0 | $ 0 | 0 |  |  |  |  |
Number of operating segments | segment |  |  |  | 2 |  |  |  |  |  |
Loans held for investment, accrued interest receivable |  | 107,200,000 |  | $ 107,200,000 |  | 73,700,000 |  |  |  |
Financing Receivable Accrued Interest After Allowance For Credit Loss Statement Of Financial Position Extensible List Not Disclosed (Flag) |  |  |  | true |  |  |  |  |  |
Revolving loans converted to term |  |  |  | $ 0 |  | 0 |  |  |  |
Sandy Spring |  |  |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |  |  |
Unpaid principle balance of CRE loans acquired | $ 2,000,000,000 |  |  |  |  |  |  |  |  |
Commercial Portfolio Segment [Member] |  |  |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |  |  |
Total Allowance for credit losses |  | $ 257,403,000 | $ 131,139,000 | $ 257,403,000 | $ 131,139,000 | $ 148,887,000 |  | $ 162,908,000 | $ 110,528,000 | $ 105,896,000
CRE | Sandy Spring |  |  |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |  |  |
LHFS |  |  |  |  |  |  | $ 1,839,968,000 |  |  |
Gain on CRE loan sale | $ 15,700,000 |  |  |  |  |  |  |  |  |

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