DERIVATIVES - Schedule of Derivative Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Derivative Assets
Total derivative assets	$ 984	$ 449
Less: Gross amounts offset in the Consolidated Balance Sheets	(107)	(87)
Less: Cash collateral applied	(70)	(45)
Total net derivative fair values presented in the Consolidated Balance Sheets	807	317
Derivative Liabilities
Derivative Liabilities	322	415
Less: Gross amounts offset in the Consolidated Balance Sheets	(107)	(87)
Less: Cash collateral applied	(95)	(36)
Total net derivative fair values presented in the Consolidated Balance Sheets	120	292
Derivatives not designated as hedging instruments:
Derivative Assets
Total derivative assets	983	444
Derivative Liabilities
Derivative Liabilities	322	415
Interest rate contracts
Derivative Assets
Total derivative assets	773	306
Derivative Liabilities
Derivative Liabilities	133	277
Interest rate contracts | Derivatives designated as hedging instruments:
Derivatives, Fair Value [Line Items]
Notional amount	29,846	12,050
Derivative Assets
Total derivative assets	1	5
Derivative Liabilities
Derivative Liabilities	0	0
Interest rate contracts | Derivatives not designated as hedging instruments:
Derivatives, Fair Value [Line Items]
Notional amount	142,386	117,076
Derivative Assets
Total derivative assets	772	301
Derivative Liabilities
Derivative Liabilities	133	277
Foreign exchange contracts
Derivative Assets
Total derivative assets	174	129
Derivative Liabilities
Derivative Liabilities	166	113
Foreign exchange contracts | Derivatives not designated as hedging instruments:
Derivatives, Fair Value [Line Items]
Notional amount	15,101	9,866
Derivative Assets
Total derivative assets	174	129
Derivative Liabilities
Derivative Liabilities	166	113
Other contracts
Derivative Assets
Total derivative assets	37	14
Derivative Liabilities
Derivative Liabilities	23	25
Other contracts | Derivatives not designated as hedging instruments:
Derivatives, Fair Value [Line Items]
Notional amount	6,868	3,555
Derivative Assets
Total derivative assets	37	14
Derivative Liabilities
Derivative Liabilities	$ 23	$ 25