DERIVATIVES - Effect of Customer Derivatives and Economic Hedges on Net Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	$ 178	$ 95	$ 534	$ 167
Economic hedges | Foreign exchange and interest rate products | Customer interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	180	425	1,269	654
Economic hedges | Foreign exchange and interest rate products | Customer foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	23	(47)	(7)	(81)
Economic hedges | Foreign exchange and interest rate products | Derivative transactions to hedge interest rate risk
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	(161)	(410)	(1,246)	(627)
Economic hedges | Foreign exchange and interest rate products | Derivative transactions to hedge foreign exchange risk
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	(50)	54	49	94
Economic hedges | Foreign exchange and interest rate products | Other derivative contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	7	0	(56)	0
Economic hedges | Foreign exchange and interest rate products | Derivative transactions to hedge other derivative risk
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	(7)	0	57	0
Economic hedges | Mortgage banking fees | Residential loan commitments
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	14	11	154	16
Economic hedges | Mortgage banking fees | Derivative contracts used to hedge residential loan commitments
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	110	(9)	(19)	(5)
Economic hedges | Mortgage banking fees | Derivative contracts used to hedge residential MSRs
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	$ 62	$ 71	$ 333	$ 116