LOANS AND LEASES - Summary of Loans and Leases Portfolio (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	$ 122,581	$ 123,090
SBA Guaranteed PPP Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		4,200
FHA, VA And USDA Guaranteed Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	1,400	249
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	59,083	60,793
Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	42,842	44,173
Commercial | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	14,412	14,652
Commercial | Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	1,829	1,968
Commercial | SBA Guaranteed PPP Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	3,500
Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	63,498	62,297
Retail | Residential mortgages (2)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	20,538	19,539
Retail | Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	11,841	12,149
Retail | Automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	12,780	12,153
Retail | Education
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	12,800	12,308
Retail | Other retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	$ 5,539	$ 6,148