BORROWED FUNDS - Long Term Debt (Details) - USD ($) $ in Millions		Sep. 30, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Long-term borrowed funds	[1]	$ 10,441	$ 12,401
Parent Company | Subordinated Debt | 4.350% fixed-rate subordinated debt, due August 2025
Debt Instrument [Line Items]
Interest rate		4.35%
Long-term borrowed funds		$ 0	133
Parent Company | Subordinated Debt | 4.300% fixed-rate subordinated debt, due December 2025
Debt Instrument [Line Items]
Interest rate		4.30%
Long-term borrowed funds		$ 336	336
Parent Company | Subordinated Debt | 3.750% fixed-rate reset subordinated debt, due February 2031
Debt Instrument [Line Items]
Interest rate		3.75%
Long-term borrowed funds		$ 69	69
Parent Company | Subordinated Debt | 4.300% fixed-rate reset subordinated debt, due February 2031
Debt Instrument [Line Items]
Interest rate		4.30%
Long-term borrowed funds		$ 135	135
Parent Company | Subordinated Debt | 4.350% fixed-rate reset subordinated debt, due February 2031
Debt Instrument [Line Items]
Interest rate		4.35%
Long-term borrowed funds		$ 60	60
Parent Company | Subordinated Debt | 5.253% fixed/floating-rate senior unsecured notes, due March 2031
Debt Instrument [Line Items]
Interest rate		5.253%
Long-term borrowed funds		$ 746	0
Parent Company | Subordinated Debt | 5.718% fixed/floating-rate senior unsecured notes, due July 2032
Debt Instrument [Line Items]
Interest rate		5.718%
Long-term borrowed funds		$ 1,244	1,243
Parent Company | Subordinated Debt | 2.638% fixed-rate subordinated debt, due September 2032
Debt Instrument [Line Items]
Interest rate		2.638%
Long-term borrowed funds		$ 575	570
Parent Company | Subordinated Debt | 6.645% fixed/floating-rate senior unsecured notes, due April 2035
Debt Instrument [Line Items]
Interest rate		6.645%
Long-term borrowed funds		$ 746	745
Parent Company | Subordinated Debt | 5.641% fixed-rate reset subordinated debt, due May 2037
Debt Instrument [Line Items]
Interest rate		5.641%
Long-term borrowed funds		$ 398	398
Parent Company | Senior Unsecured Notes | 2.850% fixed-rate senior unsecured notes, due July 2026
Debt Instrument [Line Items]
Interest rate		2.85%
Long-term borrowed funds		$ 500	499
Parent Company | Senior Unsecured Notes | 5.841% fixed/floating-rate senior unsecured notes, due January 2030
Debt Instrument [Line Items]
Interest rate		5.841%
Long-term borrowed funds		$ 1,246	1,245
Parent Company | Senior Unsecured Notes | 2.500% fixed-rate senior unsecured notes, due February 2030
Debt Instrument [Line Items]
Interest rate		2.50%
Long-term borrowed funds		$ 299	299
Parent Company | Senior Unsecured Notes | 3.250% fixed-rate senior unsecured notes, due April 2030
Debt Instrument [Line Items]
Interest rate		3.25%
Long-term borrowed funds		$ 747	747
Subsidiaries | Senior Unsecured Notes | 2.250% senior unsecured notes, due April 2025
Debt Instrument [Line Items]
Interest rate		2.25%
Long-term borrowed funds		$ 0	750
Subsidiaries | Senior Unsecured Notes | 5.284% fixed/floating-rate senior unsecured notes, due January 2026
Debt Instrument [Line Items]
Interest rate		5.284%
Long-term borrowed funds		$ 0	350
Subsidiaries | Senior Unsecured Notes | 3.750% senior unsecured notes, due February 2026
Debt Instrument [Line Items]
Interest rate		3.75%
Long-term borrowed funds		$ 499	492
Subsidiaries | Senior Unsecured Notes | 4.575% fixed/floating-rate senior unsecured notes, due August 2028
Debt Instrument [Line Items]
Interest rate		4.575%
Long-term borrowed funds		$ 799	798
Subsidiaries | Federal Home Loan Bank advances
Debt Instrument [Line Items]
Weighted average rate		2.196%
Long-term borrowed funds		$ 13	53
Subsidiaries | Secured Debt
Debt Instrument [Line Items]
Securitized borrowings, weighted average interest rate		5.536%
Long-term borrowed funds		$ 2,009	3,461
Subsidiaries | Other
Debt Instrument [Line Items]
Long-term borrowed funds		$ 20	$ 18

[1] Includes amounts in consolidated VIEs. See Note 6 for additional information.