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GOODWILL AND INTANGIBLE ASSETS (Narrative) (Details) - USD ($) | 3 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024 | Apr. 01, 2025 | Dec. 31, 2024
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |
Goodwill | $ 1,726,386,000 |  | $ 1,726,386,000 |  |  | $ 1,214,053,000
Intangible Assets | 333,236,000 |  | 333,236,000 |  |  | 84,563,000
Impairment of goodwill or intangible assets |  |  | 0 |  |  |
Intangible assets, amortization expense | $ 18,145,000 | $ 5,804,000 | $ 41,976,000 | $ 13,693,000 |  |
Core Deposits [Member] | Maximum [Member] |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |
Intangible assets, amortization period (years) | 10 years |  | 10 years |  |  |
Other Intangible Assets [Member] | Minimum [Member] |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |
Intangible assets, amortization period (years) | 5 months |  | 5 months |  |  |
Other Intangible Assets [Member] | Maximum [Member] |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |
Intangible assets, amortization period (years) | 16 years |  | 16 years |  |  |
American National |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |
Goodwill |  |  |  |  |  | $ 288,842,000
Sandy Spring |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |
Goodwill | $ 512,333,000 |  | $ 512,333,000 |  | $ 512,333,000 |
Goodwill, measurement period adjustments | 15,400,000 |  |  |  |  |
Sandy Spring | Wholesale Banking |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |
Goodwill | 399,600,000 |  | 399,600,000 |  |  |
Sandy Spring | Consumer Banking |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |
Goodwill | $ 112,700,000 |  | $ 112,700,000 |  |  |

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