Quarterly report pursuant to Section 13 or 15(d)

LOANS / LEASES AND ALLOWANCE FOR CREDIT LOSSES - Narrative (Details)

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LOANS / LEASES AND ALLOWANCE FOR CREDIT LOSSES - Narrative (Details)
 3 Months Ended
Mar. 31, 2018
USD ($)
reserve
Dec. 31, 2017
USD ($)
Mar. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Loans and leases receivable net premium $ 359,000,000 $ 334,000,000    
Consumer loans 86,000,000 93,000,000    
Allowance for loan and lease losses $ (721,000,000) (691,000,000) $ (673,000,000) $ (638,000,000)
Number of days past due 30 days      
Allowance number of reserves | reserve 2      
Collateral for secured borrowings $ 33,500,000,000 31,700,000,000    
Commercial        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Allowance for loan and lease losses $ (515,000,000) (482,000,000) (480,000,000) (451,000,000)
Threshold period past due for nonperforming status 90 days      
Threshold outstanding balance for quarterly impairment evaluation $ 1,000,000.0      
Threshold period past due for write-off 90 days      
Commercial | Commercial and Industrial        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Consumer loans $ 0 0    
Consumer        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Allowance for loan and lease losses $ (206,000,000) (209,000,000) $ (193,000,000) $ (187,000,000)
Threshold period past due for write-off 120 days      
Consumer | Automobile        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Consumer loans $ 1,000,000 1,000,000    
Consumer | Home Equity        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Consumer loans 2,000,000 2,000,000    
Consumer | Residential Mortgage        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Consumer loans 82,000,000 89,000,000    
Consumer | RV and Marine FInance        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Consumer loans 1,000,000 1,000,000    
Consumer | Other Consumer        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Consumer loans $ 0 $ 0