Quarterly report pursuant to Section 13 or 15(d)

COMMITMENTS AND CONTINGENT LIABILITIES - Narrative (Details)

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COMMITMENTS AND CONTINGENT LIABILITIES - Narrative (Details)
 2 Months Ended 3 Months Ended 6 Months Ended
Jan. 17, 2012
county
Mar. 31, 2016
lawsuit
complaint
Sep. 30, 2015
USD ($)
Jun. 30, 2016
USD ($)
lawsuit
Dec. 31, 2015
USD ($)
Sep. 28, 2015
USD ($)
Mar. 30, 2012
USD ($)
Loss Contingencies [Line Items]              
Maturity period of majority of standby letters of credit       P2Y      
Maturity period of Commercial letters of credit       P90D      
Maturity period of forward contracts relating mortgage banking business       1 year      
Cyberco Litigation              
Loss Contingencies [Line Items]              
Number of lawsuits | lawsuit       2      
Fraudulent transfers alleged by Teleservices bankruptcy trustee             $ 73,000,000
Bankruptcy Court recommended judgment amount in Cyberco case, principal           $ 72,000,000  
Loss contingency period increase (decrease)     $ 38,000,000        
MERSCORP Litigation [Member]              
Loss Contingencies [Line Items]              
Number of counties | county 88            
FirstMerit Merger Litigation [Member]              
Loss Contingencies [Line Items]              
Number of lawsuits | lawsuit   5          
Number of complaints | complaint   1          
Standby Letters of Credit              
Loss Contingencies [Line Items]              
Carrying amount of deferred revenue associated with guarantees       $ 8,000,000 $ 7,000,000    
Outstanding standby letters of credit       $ 478,333,000 511,706,000    
Percentage of Outstanding standby letters of credit collateralized       82.00%      
Commercial letters-of-credit              
Loss Contingencies [Line Items]              
Outstanding standby letters of credit       $ 29,776,000 56,119,000    
Commitments to Sell Loans              
Loss Contingencies [Line Items]              
Commitments to sell residential real estate loans       1,112,000,000 $ 659,000,000    
Risk Level, Low              
Loss Contingencies [Line Items]              
Outstanding standby letters of credit       156,000,000      
Risk Level, High              
Loss Contingencies [Line Items]              
Outstanding standby letters of credit       0      
Risk Level, Medium              
Loss Contingencies [Line Items]              
Outstanding standby letters of credit       323,000,000      
Maximum              
Loss Contingencies [Line Items]              
Aggregate range of reasonably possible losses current legal proceedings       50,000,000      
Minimum              
Loss Contingencies [Line Items]              
Aggregate range of reasonably possible losses current legal proceedings       $ 0