DERIVATIVES - Effect of Customer Derivatives and Economic Hedges on Net Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	$ (7)	$ 178	$ (108)	$ 534
Economic hedges | Foreign exchange and interest rate products | Customer interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	133	180	(215)	1,269
Economic hedges | Foreign exchange and interest rate products | Derivatives hedging interest rate risk
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	(129)	(161)	227	(1,246)
Economic hedges | Foreign exchange and interest rate products | Customer foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	19	23	(97)	(7)
Economic hedges | Foreign exchange and interest rate products | Derivatives hedging foreign exchange risk
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	(11)	(50)	139	49
Economic hedges | Foreign exchange and interest rate products | Customer commodity contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	319	7	413	(56)
Economic hedges | Foreign exchange and interest rate products | Derivatives hedging commodity price risk
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	(317)	(7)	(409)	57
Economic hedges | Mortgage banking fees | Residential loan commitments
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	67	14	(171)	154
Economic hedges | Mortgage banking fees | Derivatives hedging residential loan commitments and mortgage loans held for sale, at fair value
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	(141)	110	134	(19)
Economic hedges | Mortgage banking fees | Derivative contracts used to hedge residential MSRs
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	$ 53	$ 62	$ (129)	$ 333