LOANS AND LEASES - Summary of Loans and Leases Portfolio (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	$ 131,305	$ 128,163
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	61,521	60,350
Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	45,724	44,500
Commercial | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	14,268	14,264
Commercial | Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	1,529	1,586
Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	69,784	67,813
Retail | Residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	24,211	22,822
Retail | Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	12,264	12,015
Retail | Automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	14,439	14,549
Retail | Education
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	13,306	12,997
Retail | Other retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	$ 5,564	$ 5,430