BORROWINGS - Schedule of Subordinated Debt (Details) $ in Millions	9 Months Ended
	Sep. 30, 2025 USD ($)
Debt Instrument [Line Items]
Aggregate Principal Amount Issued	$ 745
Net Proceeds	739
Carrying Value	741
Senior Notes
Debt Instrument [Line Items]
Aggregate Principal Amount Issued	500
Net Proceeds	497
Carrying Value	498
Other Subordinated Debt
Debt Instrument [Line Items]
Aggregate Principal Amount Issued	245
Net Proceeds	242
Carrying Value	$ 243
Subordinated Notes Due 2030 | Senior Notes
Debt Instrument [Line Items]
Interest Rate	5.722%
Aggregate Principal Amount Issued	$ 500
Net Proceeds	497
Carrying Value	$ 498
Subordinated Notes Due 2030 | Other Subordinated Debt
Debt Instrument [Line Items]
Basis points, interest rate, type [Extensible Enumeration]	Secured Overnight Financing Rate (SOFR) [Member]
Basis points, spread	1.93%
6.895% Fixed-To-Floating Rate Subordinated Notes due 2029 | Other Subordinated Debt
Debt Instrument [Line Items]
Interest Rate	6.895%
Aggregate Principal Amount Issued	$ 120
Net Proceeds	118
Carrying Value	$ 119
Basis points, interest rate, type [Extensible Enumeration]	Secured Overnight Financing Rate (SOFR) [Member]
Basis points, spread	2.40%
Basis points, tenor spread adjustment	0.0026
4.875% Subordinated Notes due 2025 | Other Subordinated Debt
Debt Instrument [Line Items]
Interest Rate	4.875%
Aggregate Principal Amount Issued	$ 100
Net Proceeds	98
Carrying Value	$ 100
7.413% Fixed-To-Floating Rate Subordinated Notes due December 6, 2028 | Other Subordinated Debt
Debt Instrument [Line Items]
Interest Rate	7.413%
Aggregate Principal Amount Issued	$ 25
Net Proceeds	26
Carrying Value	$ 24
Basis points, interest rate, type [Extensible Enumeration]	Secured Overnight Financing Rate (SOFR) [Member]
Basis points, spread	3.02%
Basis points, tenor spread adjustment	0.0026