LOANS AND LEASES - Summary of Loans and Leases Portfolio (Details) - USD ($) $ in Millions		Jun. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	[1],[2]	$ 113,407	$ 110,617
Loans receivable held for sale		710	718
Mortgage loans serviced for others | Banking Subsidiaries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		21,600	20,300
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		54,888	52,031
Commercial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		39,278	37,562
Commercial | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		12,528	11,308
Commercial | Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		3,082	3,161
Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		58,519	58,586
Retail | Residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		17,814	17,045
Retail | Home equity loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		1,211	1,392
Retail | Home equity lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		13,014	13,483
Retail | Home equity loans serviced by others
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		465	542
Retail | Home equity lines of credit serviced by others
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		124	149
Retail | Automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		12,517	13,204
Retail | Education
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		8,450	8,134
Retail | Credit cards
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		1,877	1,848
Retail | Other retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases		$ 3,047	$ 2,789

[1] Excluded from the table above are loans held for sale totaling $710 million and $718 million as of June 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 $21.6 billion and $20.3 billion at June 30, 2018 and December 31, 2017, respectively.