LOANS AND LEASES - Summary of Loans and Leases Portfolio (Details) - USD ($) $ in Millions		Mar. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	[1],[2]	$ 111,425	$ 110,617
Loans receivable held for sale		800	718
Mortgage loans serviced for others | Banking Subsidiaries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		20,200	20,300
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		53,144	52,031
Commercial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		38,277	37,562
Commercial | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		11,775	11,308
Commercial | Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		3,092	3,161
Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		58,281	58,586
Retail | Residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		17,346	17,045
Retail | Home equity loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		1,298	1,392
Retail | Home equity lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		13,190	13,483
Retail | Home equity loans serviced by others
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		504	542
Retail | Home equity lines of credit serviced by others
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		136	149
Retail | Automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		12,794	13,204
Retail | Education
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		8,324	8,134
Retail | Credit cards
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		1,808	1,848
Retail | Other retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		$ 2,881	$ 2,789

[1] Excluded from the table above are loans held for sale totaling $800 million and $718 million as of March 31, 2018 and December 31, 2017, respectively.

[2] Mortgage loans serviced for others by the Company’s subsidiaries are not included above, and amounted to $20.2 billion and $20.3 billion at March 31, 2018 and December 31, 2017, respectively.