DERIVATIVES - Effect of Customer Derivatives and Economic Hedges on Net Income (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income		$ 38	$ 22	$ 43	$ 32
Customer derivative contracts | Foreign Exchange and Interest Rate Products | Interest rate contract
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	[1]	(75)	83	(279)	80
Customer derivative contracts | Foreign Exchange and Interest Rate Products | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	[1]	(68)	78	(57)	96
Customer derivative contracts | Mortgage Banking Fees | Residential loan commitments
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	[2]	1	(2)	0	3
Economic hedges | Foreign Exchange and Interest Rate Products | Interest rate contract
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	[1]	90	(71)	306	(56)
Economic hedges | Foreign Exchange and Interest Rate Products | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	[1]	92	(71)	75	(85)
Economic hedges | Mortgage Banking Fees | Forward sale contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amounts Recognized in Noninterest Income	[2]	$ (2)	$ 5	$ (2)	$ (6)

[1] Reported in foreign exchange and interest rate products on the Consolidated Statements of Operations.

[2] Reported in mortgage banking fees on the Consolidated Statements of Operations.