DERIVATIVES - Effect of Customer Derivatives and Economic Hedges on Net Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	$ 356	$ 72
Economic hedges | Foreign exchange and interest rate products | Customer interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	1,026	229
Economic hedges | Foreign exchange and interest rate products | Customer foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	(30)	(34)
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	(1,021)	(217)
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	99	40
Economic hedges | Mortgage banking fees | Residential loan commitments
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	140	5
Economic hedges | Mortgage banking fees | Forward sale contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	(129)	4
Economic hedges | Mortgage banking fees | Derivative contracts used to hedge residential MSRs
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	$ 271	$ 45