DERIVATIVES - Amounts Recorded in Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Derivative [Line Items]
Cumulative amount of fair value hedging adjustments included in the carrying amount of the hedged items	$ (8)	$ (17)
Closed Portfolios
Derivative [Line Items]
Carrying amount of hedged assets	4,800	4,000
Amortized cost	6,700	5,900
Cumulative basis adjustment	95	39
Total debt securities available for sale, at fair value
Derivative [Line Items]
Carrying amount of hedged assets	10,510	7,253
Cumulative amount of fair value hedging adjustments included in the carrying amount of the hedged assets	176	60
Long-term borrowed funds
Derivative [Line Items]
Carrying amount of hedged liabilities	491	483
Cumulative amount of fair value hedging adjustments included in the carrying amount of the hedged items	$ (8)	$ (17)