COMMITMENTS AND CONTINGENT LIABILITIES - Commitments to Extend Credit (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Commercial and industrial
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contract amount represents credit risk	$ 53,943	$ 47,736
Consumer loan portfolio
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contract amount represents credit risk	23,763	21,659
Commercial real estate
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contract amount represents credit risk	6,450	4,036
Standby letters of credit and guarantees on industrial revenue bonds
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contract amount represents credit risk	$ 1,409	$ 895