DERIVATIVES - Effect of Customer Derivatives and Economic Hedges on Net Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	$ 95	$ 38	$ 167	$ 43
Economic hedges | Foreign exchange and interest rate products | Customer interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	425	(75)	654	(279)
Economic hedges | Foreign exchange and interest rate products | Customer foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	(47)	(68)	(81)	(57)
Economic hedges | Foreign exchange and interest rate products | Derivatives transactions to hedge interest rate risk
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	(410)	90	(627)	306
Economic hedges | Foreign exchange and interest rate products | Derivatives transactions to hedge foreign exchange risk
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	54	92	94	75
Economic hedges | Mortgage banking fees | Residential loan commitments
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	11	1	16	0
Economic hedges | Mortgage banking fees | Forward sale contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	(9)	(2)	(5)	(2)
Economic hedges | Mortgage banking fees | Interest rate derivative contracts used to hedge residential MSRs
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	$ 71	$ 0	$ 116	$ 0