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ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - OCI and tax effects (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Pre-Tax Amount      
Realized loss on foreign currency transactions $ 1.9   $ 1.0
Other comprehensive income (loss), before tax 64.6 $ (34.0) (124.7)
Tax (Expense) Benefit      
Realized loss on foreign currency transactions, tax   0.5  
Other comprehensive income (loss), tax 0.2 2.4 0.2
Net-of-Tax Amount      
Realized loss on foreign currency transactions reclassified into other expense 1.9 0.5 1.0
Other comprehensive income (loss) 64.8 (31.6) (124.5)
Foreign Currency      
Pre-Tax Amount      
Unrealized foreign currency translation adjustment arising during the period 66.8 (18.3) (127.5)
Tax (Expense) Benefit      
Unrealized foreign currency translation adjustment arising during the period, tax 0.2 1.8 (0.2)
Net-of-Tax Amount      
Unrealized foreign currency translation adjustment arising during the period, net of tax 67.0 (16.5) (127.7)
Realized net (gain) loss reclassified into equity in earnings of non-consolidated entities, net of tax 1.9 0.5  
Pension and Other Benefit Adjustments, Net Gain or Loss      
Pre-Tax Amount      
Unrealized foreign currency translation adjustment arising during the period (4.1) (16.1) 3.8
Tax (Expense) Benefit      
Unrealized foreign currency translation adjustment arising during the period, tax   0.6 0.4
Net-of-Tax Amount      
Unrealized foreign currency translation adjustment arising during the period, net of tax $ (4.1) (15.5) 4.2
Unrealized Gain (Loss) from Equity Method Investees' Cash Flow Hedge      
Pre-Tax Amount      
Unrealized foreign currency translation adjustment arising during the period   (0.1) 0.2
Realized net (gain) loss reclassified into equity in earnings of non-consolidated entities, before tax     (2.2)
Net-of-Tax Amount      
Unrealized foreign currency translation adjustment arising during the period, net of tax   $ (0.1) 0.2
Realized net (gain) loss reclassified into equity in earnings of non-consolidated entities, net of tax     $ (2.2)