LOANS AND LEASES - Nonaccrual Loans by Loan Class (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans and leases with no ACL	$ 78	$ 166
Total nonaccrual loans and leases	1,697	931
Commercial \| Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans and leases with no ACL	65	76
Total nonaccrual loans and leases	1,046	562
Commercial \| Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans and leases with no ACL	8	81
Total nonaccrual loans and leases	265	133
Commercial \| Lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans and leases with no ACL	2	4
Total nonaccrual loans and leases	6	8
Consumer \| Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans and leases with no ACL	3	5
Total nonaccrual loans and leases	240	107
Consumer \| Automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans and leases with no ACL	0	0
Total nonaccrual loans and leases	8	6
Consumer \| Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans and leases with no ACL	0	0
Total nonaccrual loans and leases	129	113
Consumer \| RV and marine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans and leases with no ACL	0	0
Total nonaccrual loans and leases	2	2
Consumer \| Other consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans and leases with no ACL	0	0
Total nonaccrual loans and leases	$ 1	$ 0