LOANS AND LEASES - Summary of Loans and Leases Portfolio (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	$ 116,838,000,000	$ 116,660,000,000
Loans receivable held for sale	2,200,000,000	1,300,000,000
SBA Loans Serviced For Others | Banking and Other Subsidiaries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	18,000,000	0
Mortgage loans serviced for others | Banking and Other Subsidiaries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	72,500,000,000	69,600,000,000
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	56,963,000,000	56,783,000,000
Commercial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	41,156,000,000	40,857,000,000
Commercial | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	13,123,000,000	13,023,000,000
Commercial | Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	2,684,000,000	2,903,000,000
Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	59,875,000,000	59,877,000,000
Retail | Residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	19,192,000,000	18,978,000,000
Retail | Home equity loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	938,000,000	1,073,000,000
Retail | Home equity lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	12,266,000,000	12,710,000,000
Retail | Home equity loans serviced by others
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	348,000,000	399,000,000
Retail | Home equity lines of credit serviced by others
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	88,000,000	104,000,000
Retail | Automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	12,000,000,000	12,106,000,000
Retail | Education
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	9,305,000,000	8,900,000,000
Retail | Credit cards
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	2,046,000,000	1,991,000,000
Retail | Other retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	$ 3,692,000,000	$ 3,616,000,000