INVESTMENT SECURITIES - Narrative (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Debt Securities, Available-for-sale [Line Items]
AFS investment securities	$ 14,891,506	$ 13,580,285
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
AFS investment securities	1,498,059	1,544,147
U.S. Treasuries | Asset Pledged as Collateral
Debt Securities, Available-for-sale [Line Items]
AFS investment securities	$ 309,800	$ 250,600