DEPOSITS AND OTHER CUSTOMER ACCOUNTS (Narrative) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Financial Instruments Owned and Pledged as Collateral [Line Items]
Securities pledged as collateral, fair value	$ 5,000.0	$ 7,500.0
Demand deposit overdrafts that have been reclassified as loan balances	133.5	79.2
CD in denominations greater than $250,000	1,200.0	1,500.0
Public fund deposits
Financial Instruments Owned and Pledged as Collateral [Line Items]
Securities pledged as collateral, fair value	$ 3,800.0	$ 3,500.0