DERIVATIVES - Schedule of Derivative Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Derivative Assets
Derivative assets	$ 1,266	$ 449
Less: Gross amounts offset in the Consolidated Balance Sheets	(122)	(87)
Less: Cash collateral applied	(117)	(45)
Total net derivative fair values presented in the Consolidated Balance Sheets	1,027	317
Derivative Liabilities
Derivative Liabilities	394	415
Less: Gross amounts offset in the Consolidated Balance Sheets	(122)	(87)
Less: Cash collateral applied	(111)	(36)
Total net derivative fair values presented in the Consolidated Balance Sheets	161	292
Derivatives not designated as hedging instruments:
Derivative Assets
Derivative assets	1,266	444
Derivative Liabilities
Derivative Liabilities	391	415
Interest rate contracts
Derivative Assets
Derivative assets	993	306
Derivative Liabilities
Derivative Liabilities	175	277
Interest rate contracts | Derivatives designated as hedging instruments:
Derivatives, Fair Value [Line Items]
Notional amount	31,596	12,050
Derivative Assets
Derivative assets	0	5
Derivative Liabilities
Derivative Liabilities	3	0
Interest rate contracts | Derivatives not designated as hedging instruments:
Derivatives, Fair Value [Line Items]
Notional amount	140,652	117,076
Derivative Assets
Derivative assets	993	301
Derivative Liabilities
Derivative Liabilities	172	277
Foreign exchange contracts
Derivative Assets
Derivative assets	224	129
Derivative Liabilities
Derivative Liabilities	195	113
Foreign exchange contracts | Derivatives not designated as hedging instruments:
Derivatives, Fair Value [Line Items]
Notional amount	12,905	9,866
Derivative Assets
Derivative assets	224	129
Derivative Liabilities
Derivative Liabilities	195	113
Other contracts
Derivative Assets
Derivative assets	49	14
Derivative Liabilities
Derivative Liabilities	24	25
Other contracts | Derivatives not designated as hedging instruments:
Derivatives, Fair Value [Line Items]
Notional amount	9,382	3,555
Derivative Assets
Derivative assets	49	14
Derivative Liabilities
Derivative Liabilities	$ 24	$ 25