LOANS AND LEASES - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for sale	$ 325	$ 256
Other loans held for sale	40	25
Pre-tax income on leveraged leases	2	2	$ 3
Income tax expense on income on leveraged leases	1	1	$ 1
Retail branches
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans sold during the period		1,000
Residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans pledged as collateral for FHLB borrowed funds	23,200	22,000
Loans pledged as collateral to support the contingent ability to borrow at the FRB discount window	15,900	11,800
Commercial loan syndication
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other loans held for sale	40	25
Automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans purchased during period	1,300	1,700
Residential portfolio segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans purchased during period	1,100	1,900
Mortgage loans sold	273	126
Student loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans purchased during period	957	59
Loans sold during the period		357
Credit cards
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans sold during the period	41
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage loans sold	401
Loans sold during the period		301
Level 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for sale	325	256
Other loans held for sale	0	0
Residential loans held for sale | Level 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for sale	268	213
Commercial real estate loans held for sale | Level 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for sale	$ 57	$ 43