Quarterly report pursuant to Section 13 or 15(d)

DERIVATIVE FINANCIAL INSTRUMENTS - Narrative (Details)

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DERIVATIVE FINANCIAL INSTRUMENTS - Narrative (Details)
 3 Months Ended 9 Months Ended
Sep. 30, 2016
USD ($)
Sep. 30, 2015
USD ($)
Sep. 30, 2016
USD ($)
group
Sep. 30, 2015
USD ($)
Jun. 30, 2016
USD ($)
Dec. 31, 2015
USD ($)
Derivative [Line Items]            
Increase (decrease) to net interest income due to derivative adjustment $ 18,000,000 $ 28,000,000 $ 58,000,000 $ 79,000,000    
Gain (loss) to be reclassified during next 12 months, net 1,000,000   1,000,000      
Purchase of interest rate caps and derivative financial instruments, notional value 12,000,000,000   12,000,000,000      
Total notional amount corresponds to trading assets, fair value 8,000,000   8,000,000      
Notional amount corresponds to trading liabilities, fair value (less than) 1,000,000   1,000,000      
Credit risks from interest rate swaps used for trading purposes 391,000,000   $ 391,000,000     $ 224,000,000
Number of primary groups | group     2      
Aggregate credit risk, net of collateral 28,000,000   $ 28,000,000     15,000,000
Investment securities and cash collateral pledged by Huntington 251,000,000   251,000,000      
Investment securities and cash collateral pledged to Huntington 115,000,000   115,000,000      
Swap            
Derivative [Line Items]            
Derivative Liability 7,000,000   7,000,000      
Derivative used in trading activity            
Derivative [Line Items]            
Net derivative asset (liability) 76,000,000   76,000,000     76,000,000
Derivative financial instruments used by Huntington on behalf of customers including offsetting derivatives, notional value 19,600,000,000   19,600,000,000     14,600,000,000
Derivative used in Mortgage Banking Activities            
Derivative [Line Items]            
Purchase of interest rate caps and derivative financial instruments, notional value 200,000,000   200,000,000     500,000,000
Gains (losses) related to derivative instruments Included in total MSR (1,000,000) $ 6,000,000 17,000,000 $ 2,000,000    
Net derivative asset (liability) 11,104,000   11,104,000     7,730,000
Share Swap Economic Hedge            
Derivative [Line Items]            
Purchase of interest rate caps and derivative financial instruments, notional value         $ 20,000,000  
Derivative, Fair Value, Net 2,000,000   2,000,000      
Other Credit Derivatives            
Derivative [Line Items]            
Derivative Asset, Notional Amount $ 560,000,000   $ 560,000,000     $ 344,000,000