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
Jun. 30, 2018
USD ($)
reserve
Mar. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Jun. 30, 2017
USD ($)
Mar. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Loans and leases receivable net premium $ 372,000,000   $ 334,000,000      
Consumer loans 84,000,000   93,000,000      
Allowance for loan and lease losses $ (741,000,000) $ (721,000,000) (691,000,000) $ (668,000,000) $ (673,000,000) $ (638,000,000)
Number of days past due 30 days          
Allowance number of reserves | reserve 2          
Collateral for secured borrowings $ 34,100,000,000   31,700,000,000      
Commercial            
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Allowance for loan and lease losses $ (531,000,000) (515,000,000) (482,000,000) (475,000,000) (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 $ (210,000,000) $ (206,000,000) (209,000,000) $ (193,000,000) $ (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 $ 0   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 81,000,000   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