COMMITMENTS AND CONTINGENT LIABILITIES - Commitments to Extend Credit (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Commercial
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contract amount represents credit risk	$ 17,377	$ 17,149
Consumer
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contract amount represents credit risk	15,129	14,974
Commercial Real Estate [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contract amount represents credit risk	1,302	1,188
Standby letters of credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contract amount represents credit risk	644	676
Commercial | Commercial letters-of-credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contract amount represents credit risk	$ 9	$ 14