Quarterly report pursuant to Section 13 or 15(d)

AVAILABLE-FOR-SALE AND OTHER SECURITIES - Narrative (Details)

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AVAILABLE-FOR-SALE AND OTHER SECURITIES - Narrative (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]        
Available For Sale Securities Transferred To Held To Maturity Securities $ 1,000.0   $ 1,000.0  
Pledged investment securities to secure public and trust deposits, trading account liabilities, US Treasury demand notes and security repurchase agreements 5,400.0   5,400.0  
Unrealized Net Losses Recognized In Oci At Time Of Transfer Of Available For Sale Securities Transferred To Held To Maturity Securities 13.5      
Nonmarketable equity securities        
Schedule of Available-for-sale Securities [Line Items]        
Stock issued by Federal Reserve Banks included in other securities 298.0   298.0 $ 299.0
Federal Home Loan Bank of Cincinnati | Nonmarketable equity securities        
Schedule of Available-for-sale Securities [Line Items]        
Stock issued by the Federal Home Loan Bank included in other securities 287.0   $ 287.0 $ 249.0
Commercial        
Schedule of Available-for-sale Securities [Line Items]        
Contractually Specified Servicing Fees, Late Fees, and Ancillary Fees Earned in Exchange for Servicing Financial Assets $ 3.0 $ 2.0