DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES - Amounts Recorded on Balance Sheet Related to Fixed-to-Floating Interest Rate Swaps (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Fixed-to-floating interest rate swaps
Derivative [Line Items]
Carrying amount of the hedged assets (liabilities)	$ (2,413)	$ (2,688)
Long-term debt
Derivative [Line Items]
Discontinued hedge, cumulative adjustment	35	37
Long-term debt | Fixed-to-floating interest rate swaps
Derivative [Line Items]
Cumulative amount of fair value hedging adjustment included in the carrying amount of the hedged asset (liabilities)	$ (111)	$ (139)