LOANS AND LEASES - Summary of Loans and Leases Portfolio (Details) - USD ($) $ in Millions		Sep. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	[1],[2]	$ 114,720	$ 110,617
Loans receivable held for sale		1,300	718
Mortgage loans serviced for others | Banking Subsidiaries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		67,500	20,300
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		55,405	52,031
Commercial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		39,770	37,562
Commercial | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		12,630	11,308
Commercial | Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		3,005	3,161
Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		59,315	58,586
Retail | Residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		18,493	17,045
Retail | Home equity loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		1,131	1,392
Retail | Home equity lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		12,863	13,483
Retail | Home equity loans serviced by others
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		429	542
Retail | Home equity lines of credit serviced by others
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		114	149
Retail | Automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		12,255	13,204
Retail | Education
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		8,712	8,134
Retail | Credit cards
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		1,911	1,848
Retail | Other retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		$ 3,407	$ 2,789

[1] Excluded from the table above are loans held for sale totaling $1.3 billion and $718 million as of September 30, 2018 and December 31, 2017, respectively.

[2] Mortgage loans serviced for others by the Company’s subsidiaries are not included above, and amounted to $67.5 billion and $20.3 billion at September 30, 2018 and December 31, 2017, respectively.