BORROWED FUNDS - Long Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Long-term borrowed funds	$ 15,887	$ 6,932
Parent company
Debt Instrument [Line Items]
Long-term borrowed funds	$ 3,336
Parent company | Subordinated Debt | 4.150% fixed rate subordinated debt, due 2022
Debt Instrument [Line Items]
Interest rate	4.15%
Long-term borrowed funds	$ 0	168
Parent company | Subordinated Debt | 3.750% fixed rate subordinated debt due 2024
Debt Instrument [Line Items]
Interest rate	3.75%
Long-term borrowed funds	$ 90	90
Parent company | Subordinated Debt | 4.023% fixed rate subordinated debt, due 2024
Debt Instrument [Line Items]
Interest rate	4.023%
Long-term borrowed funds	$ 17	17
Parent company | Subordinated Debt | 4.350% fixed rate subordinated debt, due 2025
Debt Instrument [Line Items]
Interest rate	4.35%
Long-term borrowed funds	$ 133	133
Parent company | Subordinated Debt | 4.300% fixed rate subordinated debt, due 2025
Debt Instrument [Line Items]
Interest rate	4.30%
Long-term borrowed funds	$ 336	336
Parent company | Subordinated Debt | 3.750% Fixed Rate 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 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 Subordinated Debt, Due February 2031
Debt Instrument [Line Items]
Interest rate	4.35%
Long-term borrowed funds	$ 61	$ 60
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	$ 556	$ 550
Parent company | Subordinated Debt | Subordinated Debt, 5.641% Fixed Rate, Due May 2037
Debt Instrument [Line Items]
Interest rate	5.641%
Long-term borrowed funds	$ 397	0
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	$ 498	498
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	$ 298	298
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	$ 746	745
CBNA and Other Subsidiaries
Debt Instrument [Line Items]
Long-term borrowed funds	$ 12,551
CBNA and Other Subsidiaries | Senior Unsecured Notes | 3.250% senior unsecured notes, due February 2022
Debt Instrument [Line Items]
Interest rate	3.25%
Long-term borrowed funds	$ 0	700
CBNA and Other Subsidiaries | Senior Unsecured Notes | 0.845% Floating-Rate Senior Unsecured Notes, Due February 2022
Debt Instrument [Line Items]
Interest rate	0.845%
Long-term borrowed funds	$ 0	300
CBNA and Other Subsidiaries | Senior Unsecured Notes | 1.318 Floating-Rate Senior Unsecured Notes, Due May 2022
Debt Instrument [Line Items]
Interest rate	1.318%
Long-term borrowed funds	$ 0	250
CBNA and Other Subsidiaries | Senior Unsecured Notes | 2.650% senior unsecured notes, due May 2022
Debt Instrument [Line Items]
Interest rate	2.65%
Long-term borrowed funds	$ 0	503
CBNA and Other Subsidiaries | Senior Unsecured Notes | 3.700% senior unsecured notes, due March 2023
Debt Instrument [Line Items]
Interest rate	3.70%
Long-term borrowed funds	$ 497	512
CBNA and Other Subsidiaries | Senior Unsecured Notes | 5.676% Floating-Rate Senior Unsecured Notes, Due March 2023
Debt Instrument [Line Items]
Interest rate	5.676%
Long-term borrowed funds	$ 250	250
CBNA and Other Subsidiaries | Senior Unsecured Notes | 2.250% senior unsecured notes, due April 2025
Debt Instrument [Line Items]
Interest rate	2.25%
Long-term borrowed funds	$ 748	746
CBNA and Other Subsidiaries | Senior Unsecured Notes | Senior Unsecured Notes, 4.119% Fixed/Floating-Rate, Due May 2025
Debt Instrument [Line Items]
Interest rate	4.119%
Long-term borrowed funds	$ 648	0
CBNA and Other Subsidiaries | Senior Unsecured Notes | Senior Unsecured Notes, 6.064% Fixed/Floating-Rate, Due October 2025
Debt Instrument [Line Items]
Interest rate	6.064%
Long-term borrowed funds	$ 598	0
CBNA and Other Subsidiaries | Senior Unsecured Notes | 3.750% senior unsecured notes, due February 2026
Debt Instrument [Line Items]
Interest rate	3.75%
Long-term borrowed funds	$ 475	524
CBNA and Other Subsidiaries | Senior Unsecured Notes | Senior Unsecured Notes, 4.575% Fixed/Floating-Rate, Due August 2028
Debt Instrument [Line Items]
Interest rate	4.575%
Long-term borrowed funds	$ 797	0
CBNA and Other Subsidiaries | Federal Home Loan advances
Debt Instrument [Line Items]
Weighted average interest rate	4.283%
Long-term borrowed funds	$ 8,519	19
CBNA and Other Subsidiaries | Other
Debt Instrument [Line Items]
Long-term borrowed funds	$ 19	$ 29