INVESTMENT SECURITIES - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
Debt Securities, Available-for-sale [Line Items]
AFS investment securities	$ 14,885,573	$ 13,580,285
US Treasury Securities And Collateralized Mortgage-Backed Securities | Asset Pledged as Collateral
Debt Securities, Available-for-sale [Line Items]
AFS investment securities	308,000
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
AFS investment securities	$ 1,561,091	1,544,147
U.S. Treasuries | Asset Pledged as Collateral
Debt Securities, Available-for-sale [Line Items]
AFS investment securities		$ 250,600