LOANS AND LEASES - Summary of Loans and Leases Portfolio (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	$ 143,188	$ 145,959
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	72,823	74,445
Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	43,951	44,974
Commercial | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	28,872	29,471
Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	70,365	71,514
Retail | Residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	31,512	31,332
Retail | Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	15,113	15,040
Retail | Automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	7,277	8,258
Retail | Education
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	11,646	11,834
Retail | Other retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	$ 4,817	$ 5,050