Quarterly report [Sections 13 or 15(d)]

GOODWILL AND INTANGIBLE ASSETS (Schedule of Goodwill and Intangible Assets by Operating Segment) (Details)

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GOODWILL AND INTANGIBLE ASSETS (Schedule of Goodwill and Intangible Assets by Operating Segment) (Details) - USD ($)
$ in Thousands
Sep. 30, 2025
Apr. 01, 2025
Dec. 31, 2024
Finite-Lived Intangible Assets [Line Items]      
Goodwill $ 1,726,386   $ 1,214,053
Intangible Assets 333,236   84,563
American National      
Finite-Lived Intangible Assets [Line Items]      
Goodwill     288,842
Sandy Spring      
Finite-Lived Intangible Assets [Line Items]      
Goodwill 512,333 $ 512,333  
Wholesale Banking | Sandy Spring      
Finite-Lived Intangible Assets [Line Items]      
Goodwill 399,600    
Consumer Banking | Sandy Spring      
Finite-Lived Intangible Assets [Line Items]      
Goodwill 112,700    
Operating segments | Wholesale Banking      
Finite-Lived Intangible Assets [Line Items]      
Goodwill 1,249,654   850,035
Intangible Assets 52,037   8,714
Operating segments | Wholesale Banking | Sandy Spring      
Finite-Lived Intangible Assets [Line Items]      
Goodwill 399,600    
Intangible Assets 46,300    
Operating segments | Consumer Banking      
Finite-Lived Intangible Assets [Line Items]      
Goodwill 476,732   364,018
Intangible Assets 657   778
Operating segments | Consumer Banking | Sandy Spring      
Finite-Lived Intangible Assets [Line Items]      
Goodwill 112,700    
Corporate Other      
Finite-Lived Intangible Assets [Line Items]      
Goodwill 0   0
Intangible Assets 280,542   $ 75,071
Corporate Other | Sandy Spring      
Finite-Lived Intangible Assets [Line Items]      
Intangible Assets $ 244,400