DERIVATIVES - Schedule of Derivative Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Derivative Assets
Derivative assets	$ 2,452	$ 984
Less: Gross amounts offset in the Consolidated Balance Sheets	(222)	(107)
Less: Cash collateral applied	(161)	(70)
Total net derivative fair values presented in the Consolidated Balance Sheets	2,069	807
Derivative Liabilities
Derivative Liabilities	615	322
Less: Gross amounts offset in the Consolidated Balance Sheets	(222)	(107)
Less: Cash collateral applied	(195)	(95)
Total net derivative fair values presented in the Consolidated Balance Sheets	198	120
Derivatives not designated as hedging instruments:
Derivative Assets
Derivative assets	2,450	983
Derivative Liabilities
Derivative Liabilities	614	322
Interest rate contracts
Derivative Assets
Derivative assets	1,905	773
Derivative Liabilities
Derivative Liabilities	251	133
Interest rate contracts | Derivatives designated as hedging instruments:
Derivatives, Fair Value [Line Items]
Notional amount	28,300	29,846
Derivative Assets
Derivative assets	2	1
Derivative Liabilities
Derivative Liabilities	1	0
Interest rate contracts | Derivatives not designated as hedging instruments:
Derivatives, Fair Value [Line Items]
Notional amount	154,654	142,386
Derivative Assets
Derivative assets	1,903	772
Derivative Liabilities
Derivative Liabilities	250	133
Foreign exchange contracts
Derivative Assets
Derivative assets	299	174
Derivative Liabilities
Derivative Liabilities	261	166
Foreign exchange contracts | Derivatives not designated as hedging instruments:
Derivatives, Fair Value [Line Items]
Notional amount	16,032	15,101
Derivative Assets
Derivative assets	299	174
Derivative Liabilities
Derivative Liabilities	261	166
TBA contracts
Derivative Assets
Derivative assets	18
Derivative Liabilities
Derivative Liabilities	47
TBA contracts | Derivatives not designated as hedging instruments:
Derivatives, Fair Value [Line Items]
Notional amount	12,156	0
Derivative Assets
Derivative assets	18	0
Derivative Liabilities
Derivative Liabilities	47	0
Other contracts
Derivative Assets
Derivative assets	230	37
Derivative Liabilities
Derivative Liabilities	56	23
Other contracts | Derivatives not designated as hedging instruments:
Derivatives, Fair Value [Line Items]
Notional amount	6,746	6,868
Derivative Assets
Derivative assets	230	37
Derivative Liabilities
Derivative Liabilities	$ 56	$ 23